This artificial water reservoir located at the altitude of 925 m was built on the Kaplický stream in 1836 for the purposes of timber floating from Boubín forests to the glass-works in Lenora. Its area is 0,37 hectares and its depth amounts to four metres. This technical structure still served to timber floating after the World War II. On the dam there is a cottage of the guards of the National Nature Reserve Boubín Virgin Forest, the benches and tables for visitors and the starting point of the instructional path round the core of the virgin forest.