Počúvadlianske jazero ( Pockhauser pond ), one of the preserved tajchy
The tajchy (singular tajch , from the German word pond ) are a reservoir system in the Štiavnické vrchy mountains around the town of Banská Štiavnica (German Schemnitz ) in central Slovakia . Most were built in the 18th century to generate energy for the local silver mines. At times there were 60 of these reservoirs, which were connected by canals and tunnels with a length of more than 100 km, today 24 are still present and are largely used for recreational activities. Because of their historical importance, they have been a UNESCO World Heritage Site since 1993 , along with the town of Banská Štiavnica and other technical monuments in the area.