English: Vlasina Lake is a semi-artificial lake in Southeast Serbia. Lying at an altitude of 1,204 metres, with an area of 15 square kilometres. It is the highest and largest artificial lake in Serbia. Vlasina lake was created in 1947–51 when the peat bog Vlasinsko blato (Vlasina mud) was closed off by a dam and submerged by the waters of incoming rivers, chiefly the Vlasina. One of the lake's most famous features are the floating islands, occurring when at high water level loose chunks of peat 0.5 to 2 metres thick, break off the shore. Driven by the wind, they float from one shore of the lake to another, carrying the flora and fauna. However, most of the time those islands are anchored along the shore. The lakes are overgrown with dense vegetation, including downy birch (Betula pubescens), which has the status of an endangered species. By the decision of Government of Serbia in 2006, the Vlasina region is protected as a nature preserve of special interest at category I.