(Polish Olza , Czech Olše )
Silesian Voivodeship , Poland
Moravian-Silesian Kraj , Czech Republic
|Drain over||Or → Stettiner Haff|
|source||near Istebna in the Silesian Beskids below the Gańczorka and Karolówka|
|muzzle||near Olza on the Polish-Czech border in the Oder
|Height difference||687 m|
|Bottom slope||6.9 ‰|
|length||99 kmor 86.2 km|
|10 m³ / s
7 m³ / s
|Left tributaries||Lomná , Jasení , Kopytná , Tyra , Ropičanka , Stonávka , Karvinský potok , Lutyňka|
|Right tributaries||Hluchová , Piotrówka / Petrůvka|
|Medium-sized cities||Třinec , Cieszyn , Český Těšín , Karviná , Bohumín|
For centuries the river lay in the middle of the Duchy of Teschen in Austrian Silesia . After 1918, the area along the river was divided between Poles and Czechs, as they could not agree on who they belonged to.
The demarcation on the Olsa was a result of the First World War and the collapse of the Austro-Hungarian monarchy in 1918. Because both Poland and Czechoslovakia claimed the entire Olsa region and the Hultschiner Ländchen , in 1919 the Polish-Czechoslovak border war broke out . Even after the conflict was resolved, it continued to smolder covertly, so that Poland enforced its claims in 1938 immediately after the Munich Agreement . After the German occupation of Poland in 1939, the entire Olsa area became part of the German Empire . After the end of the Second World War , the course of the border was restored in accordance with the provisions of 1918, and a border treaty was concluded in 1958.
The Olsa rises three kilometers southwest of the Aries Mountain ( Baranowa Góra ) and the source of the Vistula at the foot of the Silesian Beskids in Poland. It flows in a westerly direction past the village of Istebna and forms the natural border between the Silesian Beskids and the Jablunkau Uplands . After about 12 km on Polish territory, your run continues behind Jasnowice, near the triangle between the Czech Republic , Poland and Slovakia , on Czech territory.
Here the river valley forms the Jablunkovská brázda. The town of Jablunkov ( Jablunkau ) lies on the Olsa , where the Lomná flows into it. Třinec ( Trzynietz ) and Teschen (Cieszyn in Polish, Český Těšín in Czech ) lie on the course of the river, which goes northwest and north . Since the end of the First World War , the river has divided this city with short interruptions. Until the end of its course, the Olsa represents the state border between Poland and the Czech Republic not far from Bohumín ( Oderberg ), only around the city of Karviná ( Karwin ) it flows exclusively on Czech territory. After 83 km the Olsa joins the Oder near the village of Olza ( Olsau ).