The deeper the miners dug, the more groundwater had to be pumped out.
To drive the pumps, the world’s biggest water engine was created here, made up of dozens of artificial reservoirs known as tajchs (historic mining reservoirs), hundreds of kilometres of surface collecting ditches and feeder channels, and 2,000 kilometres of underground shafts and adits.
Halčiansky tajch was built in the second half of the 18th century. Together with Beliansky tajch it belonged to the Geramb Mining Union, and its water powered the stamp mills and smelting works in the Kozelník valley below Banská Belá. In 1906 the union sold its property, reservoirs included, to the Hungarian state mining treasury, and the Halčiansky reservoir was then used for fish farming. On 19 April 1909 it was handed over to the Mining and Forestry Academy for fish farming and for practical teaching in fisheries.
The tajch is up to 13 m deep and 123 metres long. Today it is used for fishing and recreation. In summer it hosts the light-hearted event Výlov krokodíla (‘Catching the Crocodile’), which recalls a real incident from 1962.
