Boubínské jezírko, Reservoir in Horní Vltavice, Czechia

Boubínské jezírko is a small man-made pond on the southern slope of Boubín mountain at an elevation of about 925 meters. The water is fed by a small stream that flows continuously through the basin, and the entire area is surrounded by dense forest.

The pond was built in 1836 to aid in floating timber from the Boubín forests toward lower regions. This timber-floating operation continued until 1957, after which the water body was no longer used for commercial wood transport.

The pond's alternate name, Jezírko U pralesa ("pond by the old-growth forest"), ties it to the Boubínský prales reserve whose rangers keep a cabin on the dam. Timber was still floated across the water here in 1957, and benches and tables on the dam now serve visitors to the reserve.

The dam holds a hut of the Boubínský prales national nature reserve wardens and benches with tables for visitors. The pond lies on the Kaplický potok at 925 m on the southern slope of Boubín; trails from Horní Vltavice lead up to it.

Water continuously flows through the pond rather than sitting still, which prevents the development of zooplankton and other organisms typical of stationary lakes. This flowing-water condition makes it an unusual mountain pond where the water is always moving rather than settling into a calm state.