Crossing tower of Cologne Cathedral

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Crossing tower of Cologne Cathedral, 2014
Construction of the cathedral towers, with a clear view of the crossing tower, photo by J. H. & Th. Schönscheidt, 1865

The crossing tower of Cologne Cathedral is the third tower of Cologne Cathedral, built in 1860 and redesigned in the 1960s . It is located above the crossing and is one of those parts of the cathedral for which no medieval building plans were available. As early as the late Middle Ages, the roof of the choir had a turret , which was renewed in the Baroque style in 1744 . This roof turret had to be removed in 1812 because it was dilapidated.

An “ideal view” of the completed cathedral by Sulpiz Boisserée from 1821 envisaged a massive octagonal stone tower. This could not be realized for structural reasons, so that in 1860 a wrought-iron crossing tower was built immediately after the roof structure of Cologne Cathedral based on a design by the cathedral builder Ernst Friedrich Zwirner and plans by his deputy Richard Voigtel .

The neo-Gothic decoration of this tower, with eyelashes , pinnacles and gargoyles , was badly damaged in the Second World War , while the iron substructure remained almost undamaged. The crossing tower was given its present shape between 1965 and 1973 through a new cladding with decorative elements in the style of Art Deco . The originally at the base of the tower helmet mounted Wimperge were eight angels made covered with lead larch wood according to a design of the Cologne Dombildhauers Erlefried Hoppe replaced, for the Hubert Bruhs the wood cores of FIGS anfertigte.

The crossing tower in the first construction period

Legend of St. Ursula , Cologne School of Painting , around 1455–1460
Street scene , Jan van der Heyden , 1684

The construction of Cologne Cathedral in the Middle Ages only got a little beyond the completion of the choir in 1322 and the first two floors of the south tower. The choir was closed off to the west by a wall; essentially only the eastern pillars and the eastern walls stood from the transept.

Medieval plans like those found for most parts of the cathedral were not available for a roof turret or crossing tower. Sulpiz Boisserée , in his work with views and plans of the Cologne Cathedral, published for the first time in 1821, expressed the conviction that the medieval planning already envisaged a massive octagonal tower above the crossing. However, his assessment was based solely on comparisons with other cathedrals of the 13th century and his own aesthetic considerations.

The Cologne cathedral builder Ernst Friedrich Zwirner established in 1855 that there was nothing on the medieval components of Cologne Cathedral, especially on the two western choir pillars, to indicate that a crossing tower should be built. The corner pillars of the crossing have a solid core with a small diameter and unconnected services . The eastern pillars consist of a core faced with house stones, which is made of brick-shaped tuff , which can withstand low loads . In addition, the pillars had been erected with so little care that anchors had to be attached in 1826 to hold the pillars striving together.

Zwirner and his deputy and successor Richard Voigtel took the view that a crossing tower was necessary and was part of the profile of the entire building, with a view to other large Gothic sacred buildings such as the Amiens Cathedral , the construction of which began before that of Cologne Cathedral. Since the pillars could not have supported a massive stone tower, Voigtel suspected that no tower was planned when the foundations of the cathedral were laid.

Regardless of the question of the construction planning of the 13th century, it is certain that a roof turret was placed on the roof of the cathedral choir, which was completed in 1322, in the Middle Ages . Depictions of Cologne Cathedral from the 15th to 17th centuries always show him with the cathedral crane on the partially erected south tower, and with a roof turret on the choir.

Baroque roof turret

View of the cathedral square in Kölln , Laurenz Janscha , 1798
Cathedral courtyard , drawing and engraving by Johann Paul Josef Ritter , 1806

In 1744, a baroque roof turret with two bells was built on the roof of the choir, immediately behind the crossing . In 1809 the lower area of ​​the ridge was partially clad with lead.

In 1811, at the instigation of Sulpiz Boisserée , the city of Cologne commissioned the Hessian chief building officer Georg Moller to examine the structural damage to the cathedral, especially to the western gable of the choir and the roof turret , together with the Cologne city architect Peter Schmitz and the master builder Johannes Baptist Leidel. An inspection of the cathedral took place on September 30, 1811, during which considerable damage was found to the roof turret. The six main pillars of the ridge and most of the rest of the wood were infected by the woodworm and loosened from the association. The last roof beam at the western end of the choir had sunk in and broken due to the load from the roof turret to the south. Years earlier it had been poorly connected with narrow strips and supported with the three other beams on which the roof turret rested with sprouts against the side walls of the choir. As a result of this load, the walls had been pushed outwards, which in turn had caused cracks in the choir vault and in the gable wall. Due to the broken load-bearing beam and its own poor construction, the tower was inclined to the south-west as a whole.

As a result of the inspection, it was recommended, among other measures at the cathedral, to remove the ridge turret before winter. However, the work was not carried out immediately. It was not until June 1812 that the French prefect ordered the church council to remove the ridge turret. The demolition took place up to the part that was newly covered with lead in 1809.

At the request of the cathedral priest Michael Joseph DuMont , Boisserée designed a new roof turret 17 meters high and around 2.90 meters wide. As recently as 1816, a cost estimate submitted to the city council for the most urgent work on the cathedral contained expenses for the rebuilding of the ridge turret. Almost half of the budget was earmarked for this. However, the plans did not come to fruition.

Designed by Sulpiz Boisserée

“Ideal view” of the finished cathedral , Sulpiz Boisserée , 1821
Cologne Cathedral from the southeast , Sulpiz Boisserée, 1842

For Sulpiz Boisserée, there was no question that Cologne Cathedral had to have a central tower and that this had already been planned by the medieval builders . He dealt intensively with the dimensions of the tower, in particular with their relationship to the dimensions of the two main towers. In doing so he relied on a plan published by Hermann Crombach in 1654 based on medieval models.

On May 8, 1810, Boisserée described his approach in a letter to Johann Wolfgang von Goethe :

“What is striking and desirable about this large fragment is that wherever one part of the building is supposed to connect with the other, the individual sections protrude clearly formed into window railings, cornices, etc. and seem to strive for further development, as it were; This, and the exact measurement of the finished product, as you have proof of it in the ground plan and cross-section, made it possible for me, with an old, albeit bad, copy of the towers engraved in copper, the entire design of the building as the unknown master intended has to manufacture faithfully and reliably. Only in the side entrances and their gables, but mostly in the middle tower, I missed the individual models and conditions; At the entrance I was helped to a certain extent by a door wall on the north side that was already set up at a certain height, and then what of the main entrance was already finished or contained in that copper engraving. I had to build the middle tower from the general proportions of the whole and from the main towers designed by the master; I consulted whatever I could always get from buildings of a similar kind. Everything, like the four great pillars in the middle and the whole structure of the building itself, confirms the necessity of this third tower. But I hardly received the most general useful evidence of shapes and circumstances. Fortunately, the conditions at the Cologne cathedral are so definite and pure, and the law of shapes, however varied they may be, so firm and simple that I was able to derive strict principles for my procedure from them. "

- Sulpiz Boisserée : Letter to Johann Wolfgang von Goethe on May 8, 1810

A manuscript left by Sulpiz Boisserée shows that he greatly revised his original design after the original medieval plans of the main towers and other parts of the building were found. In 1821 he published in his work Views, Cracks and Individual Parts of the Cologne Cathedral, an “ideal view” of the completed cathedral, above which a massive octagonal crossing tower rises. This design was based on the consideration that the height of the tower above the church floor to its width determined by the dimensions of the crossing had to be in the same ratio as the height of the main towers to their width measured on the roof of the nave . This gave Boisserée a ratio of six and a half to one. In addition, in his eyes an octagonal floor plan and the openwork were spire of more determined than one third of the height of the tower by the shape of the main towers.

In Boisserée's design, the first floor of the crossing tower extends to the height of the roof ridge and has a square floor plan with bevelled corners. The second and third floors have regular octagonal floor plans. On the second floor there are glazed ogival windows, in the upper quarter with tracery , above neo-Gothic eyelashes . A corridor running around the outside has a tracery parapet, pinnacles are placed in front of the windows of the four secondary directions . On the second floor, wall pillars reach up to the ceiling, where they support a vault. The third floor is the openwork tower spire. A corridor also runs around its base, with pinnacles at all eight corners. On the top of the tower, Boisserée put a star instead of the usual finial or a cross. He assumed here that the Epiphany shrine containing the relics of the Magi is situated in the crossing under the tower.

Boisserée's design was not implemented. However, decades later, when the question of erecting a ridge turret or crossing tower became topical due to the progress made in building Cologne Cathedral, it was the basis for one of the designs by master builder Zwirner.

Zwirner and Voigtel crossing tower

planning

View of the crossing tower with details, drawing by Richard Voigtel , ca.1860

When construction work began on Cologne Cathedral in 1842, the question of building a roof turret or a crossing tower arose. In principle, there was agreement that the cathedral should be completed in exactly the way that Master Gerhard had planned in the 13th century. However, the original plans stored in the cathedral archives were lost in connection with the French occupation of Cologne and only partially recovered. The Cologne cathedral builder Ernst Friedrich Zwirner published a treatise in the first six issues of the Kölner Domblatt in 1842 with the title Past and Future of Cathedral Construction . With regard to the crossing tower, Zwirner expressed doubts that a crossing tower was planned. In his opinion, the pillars of the crossing were designed so that they only had to support the vault of the crossing. In addition, Zwirner preferred the Boisserée design over a slimmer version. In addition to the costs and the risk for the structure due to the additional load, he pointed out that a crossing tower would impair the effect of the west facade with its slender towers.

On June 18, 1853, the Prussian supervisory authority for the construction of the cathedral, the Royal Technical Building Deputation in Berlin, of which the Cologne master builder Ernst Friedrich Zwirner was a member, and discussed the execution of the four tower. Zwirner submitted four designs to the commission, one of which was an implementation of Boisserée's design, two others also envisaged a massive tower made of stone , and only the fourth was a metal construction. The commission found that a crossing tower like other cathedrals from the same era was desirable. However, she also determined that a massive tower had to be refrained from because of the poor subsurface. There was concern that the excessive load could cause the eastern piers to collapse. Even the third design, to be made from tuff , was not convincing, as its weight would have been too great for the pillars of the crossing. This meant that three of the four drafts submitted by Zwirner had to be rejected. The fourth draft envisaged an iron crossing tower that was to be clad with lead or zinc . In addition to the lower weight, the fire protection, the longer durability of iron and the lower production costs spoke in favor of the metal construction. Therefore, on June 29, 1853, the supervisory authority recommended the construction of a crossing tower with metal roofing. On April 4, 1855, Zwirner's draft was approved by royal cabinet orders.

In 1858 and 1859 Richard Voigtel, as deputy cathedral builder, made the plans for the crossing tower and carried out the structural calculations. The guideline imposed on him was that the crossing piers were to be loaded with a maximum of 530 pounds per square inch . This made it necessary to largely dispense with cast iron and to use rolled sheet metal and profile iron.

construction

Base frame with stabilizing ring, shown from above
Average of the substructure with cast iron shoes

The substructure of the crossing tower rests on the four approximately 1.30 meter thick belt arches that enclose the crossing and form a square with a side length of approximately 12.80 meters. A gusset was built into each of the four corners of the square to create an equilateral octagon as a support surface for the octagonal tower at the base. A cast iron shoe rests freely on each corner, in which a tubular receptacle is turned to accommodate a column of the substructure. The inward inclination of the columns of around 70 degrees would result in the stone support surfaces and the medieval pillars of the crossing being exposed to an outward force. This is why there is a wrought iron ring in the middle of the tower base, from which a threaded rod about eight centimeters in diameter runs to each cast iron shoe and is tightened on the outside with a nut . The system of the ring with the tie rods is attached to four further upwardly directed tie rods, which are anchored to an iron plate more than two centimeters thick above the heads of the inclined columns. In the original plan, a ring ran around the wreath of cast-iron shoes on the outside, which had an additional fastening option between two shoes, but was not realized or is no longer available today.

Cross section of the spire with details of the frame

The base is a truncated pyramid with an octagonal base surface, the fully under the roofs of the naves is hidden. Its eight columns have a wall thickness of about 5.2 centimeters, a diameter of about 54 centimeters and a length of about eight meters. They were poured upright in dam pits and turned off at both ends to fit the shoes. The substructure is protected against twisting by a system of tie rods and stabilizing rings.

The drum rests on the iron plate on the substructure. Its eight 12.40-meter-long corner pillars with a square cross-section consist of profiles made of rolled sheet metal that are more than one centimeter thick and are screwed to the base plate at the lower end. At the top they are connected to another plate, which also forms the floor of the openwork gallery. On top of this plate are in turn around eleven meters high corner pillars with a pentagonal floor plan. At its upper ends, arched lugs are screwed, which point inwards and close the tower helmet down to an entry opening.

The tower spire consists of eight lattice girders, which taper towards the top and are connected to each other at a distance of about 3.20 meters by wrought-iron belts and diagonal struts. The top of the tower is a finial made of copper , on which a gold-plated star as a symbol of the Christmas story and the Three Wise Men is not attached as in other churches . The star is shaped as an icosahedral star and has an orbital diameter of 1.80 meters. Its gold-plated surface is approximately 3.25 square meters. A certificate was placed in the finial when the crossing tower was completed in 1861.

Picture gallery

Transition from the substructure to the drum, top left the approach of the spiral staircase to the platform

  • Cast iron shoe with pipe of the substructure

  • Jig and pull rod

  • Wrench

  • Stabilizing ring over the vault of the crossing

  • Base plate of the drum, from below

The picture gallery shows from the left one of the eight cast-iron shoes in which the inwardly inclined pillars of the substructure stand. This is followed by a shot in which the pull rod and the wrought iron stabilizing ring in the middle of the substructure can be seen on the right behind the shoe. The wrench in the third picture is about two meters long. The fourth picture shows the stabilizing ring above the vault of the crossing , in the middle of the tie rods and with the cast iron pillars in the background. The horizontal and diagonal struts between the columns are clearly visible. The fifth illustration shows the base plate of the main drum , which is supported by the pillars of the substructure.

execution

The iron frame construction, like the iron roof of the nave , was made and installed by the Cölnische Maschinenbau-Actien-Gesellschaft from Cologne-Bayenthal. In June 1860 the scaffolding for the erection of the crossing tower was erected. On October 15, 1860, the 65th birthday of King Friedrich Wilhelm IV. , The committed supporter of the cathedral building, cathedral builder Ernst Friedrich Zwirner placed the gold-plated star on the finial of the four-sided tower. 214 tons of iron were used for the construction. It has a diameter of 8.80 meters and a height of 110 meters above the church floor.

On October 11, 1860, the Cologne city council decided to grant a subsidy towards the costs of covering the roof and the crossing tower. The subsidy was tied to the condition that lead was used and was intended to cover the additional costs compared to zinc cover. The covering of the crossing tower evidently deviated from this requirement with elements made of cast zinc in order to save weight. The decorations were also made of cast zinc. In the spring of 1861 the crossing tower was covered and thus completed.

Redesign after the Second World War

War damage and repairs

Cologne Cathedral with the damaged crossing tower, around 1960

The iron substructure of the four tower survived the Second World War without any significant damage. However, the zinc cast elements of the cladding with their decorations had partly crashed and partly torn by the pressure waves after explosions in the vicinity. It was not possible to repair the damaged parts or replace the missing parts.

In the report by the cathedral builder Willy Weyres on the repair work between 1955 and 1957, work on the crossing tower was promised in 1958. Weyre attributed the delay so far to other urgent work and the lack of scaffolding. For the years 1958 and 1959 it was reported that at the beginning of the work on the crossing tower a systematic investigation of the iron substructure was carried out, the static investigation is still ongoing. The corrosion damage was less than feared and the construction was described as very solid. In order to avoid disturbances inside the cathedral, transport routes for the material should be set up over the roof of the transept and then the scaffolding of the crossing tower should begin.

In 1960 the scaffolding on the north transept gable was only brought up to a height of 50 meters and the elevator required for the transport of materials and ordered one and a half years earlier was not yet ready. Therefore, only a few set-up work had been carried out on the crossing tower until then. In 1961, the long-planned work on the Vierungsturm could begin after the freight elevator had been opened for operation in April. Between June and December 1961 the zinc cladding of the tower was removed. The eyelashes , crabs and edge panels were made of cast zinc, which had become brittle over time. The feared corrosion damage due to the combination of zinc with the copper at the top of the tower did not materialize, however. Repairs were carried out on the iron framework in September and October. The framework was then derusted and the application of a protective coating began.

In 1962, rust removal was continued on the substructure of the tower and a final protective coating was applied. The cladding of the tower helmet and the figure zone should be carried out in 1963, while the cladding of the lower vertical part of the tower was not planned until 1964 for technical and financial reasons.

In 1963, parts of several services in the transept flaked off. As early as the 1920s it was noticed that the pillars of the crossing were shifting. Cathedral builder Willy Weyres was of the opinion that the wind pressure on the crossing tower could be the cause of the problems.

Modern redesign

Angel on the crossing tower of Cologne Cathedral, 2012
Enlarged representation
View from the east, 2017

After the examination of the iron substructure of the crossing tower did not reveal any significant damage, the design of the new cladding was discussed. In order to ensure a uniform appearance of the cladding of the roof and crossing tower, this should no longer be made of cast zinc, but also of lead.

On May 30, 1958, a decision was made about the design of the crossing tower. The redesign meant a radical departure from historicism of the 19th century and a move towards a modern design based on Art Deco . A rich decoration of the tower helmet was omitted. Originally, the cathedral builder Willy Weyres planned circular holes for ventilation in the tower helmet. However, this could not be realized because there was no acceptable technical solution for the drainage of penetrating water. That is why the surfaces of the spire, like those of the other roofs of the cathedral, were provided with dormers . Only in April 1964 were all questions finally clarified and the number and shape of the dormers determined. From 1965 to early 1966 the roof of the tower was covered with the dormers by a roofing company in Cologne.

In the course of this work, the scaffolding around the spire was brought up to the copper spire, so that a precise assessment was possible for the first time. Since both the finial and the gold-plated star were badly damaged, especially the holding irons were rusted, they were removed. The finial was straightened in the locksmith's shop in the cathedral building. The star was restored and fire-gilded in the workshop of the goldsmith Wilhelm Nagel . On July 18, 1966, the star was put back on the tower helmet. The scaffolding was then dismantled to the base of the tower spire.

In the crossing tower from the 19th century, the transition from the vertical part of the tower to the spire was covered by a wreath of large eyelashes . For the redesign of the cladding, it was planned to attach large angel figures made of a larch wood core clad with lead . In 1962 the cathedral sculptor Erlefried Hoppe made a model of the body of a figure and attached it to the intended location. Contrary to the impression left by a previously manufactured small model, the figure appeared too large in its original size. A much smaller second dummy and a sample of the planned cladding of the tower helmet were then attached. The samples were inspected in December 1962 by a commission which, in addition to the members of the Cologne cathedral chapter, included the art historian and Rhenish state curator Rudolf Wesenberg and the Cologne architect Gustav Bader . Regarding the angel figure, the experts' judgment was positive, regardless of its rough and poorly detailed appearance. It was assumed that the lead-clad originals would have finer detailing.

The wooden cores of the angels were made by Hubert Bruhs in 1964 and 1965 . The lead cladding was done by a roofer from the cathedral building. The lead cladding had to be designed in such a way that temperature fluctuations did not result in cracks and breaks, which would result in water penetrating the wood core. In a next step, as with the bodies of the angel figures, models of their wings were inspected and corrected at the place where they were attached. The manufacture took place in the carpentry of the cathedral building from spruce wood , which was attached to iron supporting framework and then covered with lead.

In 1967 the angels were attached to the crossing tower. In the following year, the posts of the openwork storey were boarded with wood and clad with lead. The inner surface of the helmet was clad with copper sheet. The only decorative element of the tower from 1861, besides the finial and star, was the neo-Gothic tracery parapet with three four-passports on each side of the tower. It is made of cast zinc and was clad with lead. Between 1969 and 1973, the eight surfaces of the main drum , alternating between 36 and 44 square meters, were divided into three vertical fields by wooden strips according to the subdivision of the parapet above. At the top of the parapet, the tambour was given flat segments that encircle the tower. The surfaces were gradually boarded up and clad with lead. Since the roofers of the cathedral building hut had to carry out permanent sealing work in other parts of the cathedral, the work was delayed until January 26, 1973.

Internals

Belfry

In the tambour there is a wooden bell cage with the choir bells of Cologne Cathedral , to which the angelus bell , the transformation bell and the Mett bell belong. The angelus bell and the change bell were already hanging together in the roof turret of the choir in the Middle Ages , so that today they represent the oldest completely preserved bell in Europe.

  • Mettglocke

  • Transformation bell

  • Angelus bell

Stairs and ladders

Wrought iron spiral staircase in the tambour
Stairs from the roof structure to the crossing tower

Access from the roof of the cathedral to the crossing tower was via a wooden staircase until 1973. In the course of necessary improvements to fire protection , it was replaced by an iron staircase next to the pyramid-shaped substructure. In one corner of the drum there is an ornate wrought iron spiral staircase that leads to the platform.

In the 19th century, access from the platform to the 9.80 meter high entrance to the tower was ensured by means of a hidden ladder. When the tower was redesigned in the 1960s, a vertical ladder made of stainless steel with a protective cage was installed in the middle of the platform. When looking at the cathedral from all sides, this ladder looked like a ninth pillar of the spire and was viewed by the cathedral building administration as a disruptive element in the 1990s. In 1997 the lower half of the ladder was dismantled during repair work and temporarily replaced with an aluminum ladder. In 2005, a one-piece, twelve-meter long aluminum ladder was installed that can be fully retracted into the tower helmet. It hangs on two ropes and, if necessary, is extended using an electric winch that is attached to the tower helmet and operated by radio. At the lower end of the ladder there is a round aluminum plate which, when retracted, closes the entry opening of the tower helmet.

Other fixtures

Trigonometric point on the crossing tower

The highest trigonometric point in Cologne is located on the platform of the crossing tower . Its demarcation was carried out in 1867, had not yet been established as the main towers, under the under the direction of Johann Jacob Baeyer performed European level measurement .

In 2011, a radio amplifier was installed in the crossing tower to ensure a reliable radio link for the fire brigade working at various points in the dome.

Criticism of the architecture

The modern silhouette of the crossing tower has been associated with Art Deco . The building master responsible for the cathedral, Willy Weyres , made a conscious decision in favor of a contemporary architectural style in order to see modern forms realized on the cathedral. The choice of this architectural style for the tower of a Gothic cathedral has, however, also aroused considerable criticism. This is how Philippe Villeneuve, the chief architect of the Paris Cathedral Notre-Dame , described the Cologne crossing tower as a foreign body and compared it to a "wart."

Web links

Commons : Vierungsturm of Cologne Cathedral  - collection of pictures, videos and audio files

See also

Portal: Cologne Cathedral  - Overview of Wikipedia content on the subject of Cologne Cathedral

literature

Individual evidence

  1. ^ Sulpiz Boisserée: History and description of the Cologne Cathedral, p. 30.
  2. ↑ a b Richard Voigtel: Construction of the roof rider on the intersection of the cathedral in Cologne , Sp. 313-314.
  3. ↑ a b c Ernst Friedrich Zwirner: Thirty-fifth construction report on the expansion of the Cologne Cathedral per I semester 1855 . In: Kölner Domblatt No. 123, June 3, 1855, pp. 3-4, digitizedhttp: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fdigi.ub.uni-heidelberg.de%2Fdiglit%2Fkoelnerdomblatt1855~GB%3D~IA%3D~MDZ%3D%0A~SZ%3D~doppelseiten% 3D ~ LT% 3D ~ PUR% 3D .
  4. ↑ a b c d e Richard Voigtel: Construction of the roof rider on the crossing of the cathedral in Cologne , Sp. 315-316.
  5. ^ Leonard Ennen: The Cologne Cathedral from its beginning to its completion, p. 95.
  6. ↑ a b c Leonard Ennen: The Cologne Cathedral from its beginning to its completion, p. 110.
  7. ↑ a b Leonard Ennen: The Cologne Cathedral from its beginning to its completion, pp. 107-108.
  8. ↑ a b Sulpiz Boisserée: History and description of the Cologne Cathedral, Appendix explanation of the copper plates , pp. 1–2.
  9. ↑ Leonard Ennen: The Cologne Cathedral from its beginning to its completion, p. 112.
  10. ↑ a b Sulpiz Boisserée: Via the central tower to Cologne Cathedral . Unpublished manuscript, edited from the estate in Jens Bisky: Poesie der Baukunst. Architectural aesthetics from Winckelmann to Boisserée . Springer, Heidelberg and Berlin 2000, doi : 10.1007 / 978-3-476-01498-6 , appendix pp. 442-445.
  11. ^ Leonard Ennen: The Cologne Cathedral from its beginning to its completion, pp. 284–285.
  12. ^ Sulpiz Boisserée: History and description of the Cologne Cathedral, pp. 35–36.
  13. ↑ Sulpiz Boisserée: History and description of the Cologne Cathedral, Appendix explanation of the copper plates , p. 10.
  14. ^ Sulpiz Boisserée: History and description of the Cologne Cathedral, Appendix explanation of the copper plates , pp. 17-18.
  15. ^ Ernst Friedrich Zwirner: Past and future of cathedral construction . In: Kölner Domblatt No. 1–6, 1842, here No. 6, August 7, 1842, pp. 2–3, digitizedhttp: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fdigi.ub.uni-heidelberg.de%2Fdiglit%2Fkoelnerdomblatt1842~GB%3D~IA%3D~MDZ%3D%0A~SZ%3D~doppelseiten% 3D ~ LT% 3D ~ PUR% 3D .
  16. ↑ a b c d Richard Voigtel: Construction of the roof rider on the intersection of the cathedral in Cologne , Sp. 317-318.
  17. ↑ a b c d Willy Weyres: The restoration work on the cathedral in the years 1963–1966 . In: Kölner Domblatt 1967, 26./27. Episode, pp. 93-110, here pp. 104-105, ISSN  0450-6413 .
  18. ↑ Richard Voigtel: The iron construction of the roof structure on the Dome in Cologne . In: Zeitschrift für Bauwesen 1862, Volume 12, Nr. 11-12, Sp. 487-490, digitizedhttp: //vorlage_digitalisat.test/1%3D~GB%3D~IA%3D~MDZ%3D%0A10933682~SZ%3D302~ double-sided%3D~LT%3D~PUR%3D , atlas sheets 63-64, digitizedhttp: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fdigital.zlb.de%2Fviewer%2Fimage%2F15239363_1862_07%2F65%2F~GB%3D~IA%3D~MDZ%3D%0A~SZ%3D~ double-sided% 3D ~ LT% 3D ~ PUR% 3D .
  19. ↑ Leonard Ennen: The Cologne Cathedral from its beginning to its completion, p. 264.
  20. ^ Leonard Ennen: The Cologne Cathedral from its beginning to its completion, p. 222.
  21. ^ Ernst Friedrich Zwirner: 45th building report on the cathedral building in Cologne . In: Kölner Domblatt No. 184, July 1, 1860, pp. 4–5, digitizedhttp: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fdigi.ub.uni-heidelberg.de%2Fdiglit%2Fkoelnerdomblatt1860~GB%3D~IA%3D~MDZ%3D%0A~SZ%3D~doppelseiten% 3D ~ LT% 3D ~ PUR% 3D .
  22. ↑ Ferdinand Esser II et al .: Two hundred thirty-fifth minutes of the Central-Dombau-Verein board . In: Kölner Domblatt No. 188, November 5, 1860, pp. 1–2, digitizedhttp: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fdigi.ub.uni-heidelberg.de%2Fdiglit%2Fkoelnerdomblatt1860~GB%3D~IA%3D~MDZ%3D%0A~SZ%3D~doppelseiten% 3D ~ LT% 3D ~ PUR% 3D .
  23. ↑ a b c d e Willy Weyres: The restoration work on the cathedral in 1962 . In: Kölner Domblatt 1963, 21./22. Episode, pp. 121-126, here p. 124, ISSN  0450-6413 .
  24. ^ Willy Weyres: The restoration work on the cathedral in the years 1955–1957 . In: Kölner Domblatt 1958, 14./15. Episode, pp. 97-103, here p. 101, ISSN  0450-6413 .
  25. ^ Willy Weyres: The restoration work on the cathedral in the years 1958-1959 . In: Kölner Domblatt 1959, 16./17. Episode, pp. 106-111, here p. 109, ISSN  0450-6413 .
  26. ^ Willy Weyres: The restoration work on the cathedral in the years 1959–1960 . In: Kölner Domblatt 1960, 18./19. Episode, pp. 136-138, here p. 136, ISSN  0450-6413 .
  27. ↑ a b c Willy Weyres: The restoration work on the cathedral in 1961 . In: Kölner Domblatt 1961/62, 20th episode, pp. 166–170, here pp. 168–169, ISSN  0450-6413 .
  28. ^ Willy Weyres: The restoration work on the cathedral in the years 1963–1966 . In: Kölner Domblatt 1967, 26./27. Episode, pp. 93-110, here pp. 98-99, ISSN  0450-6413 .
  29. ↑ a b Willy Weyres: The restoration work on the cathedral in the years 1967–1969 (autumn) . In: Kölner Domblatt 1969, 30th episode, pp. 113–120, here p. 118, ISSN  0450-6413 .
  30. ↑ Willy Weyres: The restoration work on the cathedral in the years 1969 (autumn) to 1971 (autumn) . In: Kölner Domblatt 1971, 33./34. Episode, pp. 175-182, here p. 179, ISSN  0450-6413 .
  31. ↑ Arnold Wolff: 15 Dombaubericht. From autumn 1971 to the end of September 1973 . In: Kölner Domblatt 1973, 36./37. Episode, pp. 35-64, here pp. 44-46, ISSN  0450-6413 .
  32. ↑ Arnold Wolff: 15 Dombaubericht. From autumn 1971 to the end of September 1973 . In: Kölner Domblatt 1973, 36./37. Episode, pp. 35-64, here p. 53, ISSN  0450-6413 .
  33. ^ Barbara Schock-Werner: 46th cathedral report. From October 2004 to September 2005 . In: Kölner Domblatt 2005, 70th episode, pp. 10–60, here pp. 26–27, ISSN  0450-6413 .
  34. ↑ Barbara Schock-Werner: 52nd cathedral report. From October 2010 to September 2011 . In: Kölner Domblatt 2011, 76th episode, pp. 129–196, here p. 147, ISSN  0450-6413 .
  35. ↑ ksta.de: How the wart on the Cologne Cathedral came about
  36. ↑ Domradio.de: Cologne crossing tower a wart

Coordinates: 50 ° 56 '28.8 "  N , 6 ° 57' 29.6"  E