Lake Sniardwy is the largest lake in Poland. It receives the water from an area about 2,400 km2, i. e. two-thirds of the basin of Great Masurian Lakes, the most important lake district in Poland, which contains about 10% of all lake area in Poland and in turn is part of Baltic lakelands in Europe. Lake Sniardwy watershed belongs to the River Pisa and finally - the River Vistuala drainage basin.

The whole Lake Sniardwy region was formed during the last glaciation about 12,000 years ago as the melting product of "dead" ice block. Hilly relief is formed by moraines, ramparts and out-wash plains; sand, gravel and clay dominate substrata.

Lake Sniardwy is the central part of Masurian Landscape Protective Area formed to protect the postglacial relief, forest and swamps with boreal and subarctic vegetation, as well as many lakes and pools. In the Protective Area several reserves occur with the stands of rare plant species and old forest; there are also waterfowl reserves like Lake Luknajno biosphere reserve with the colony of mute swan. The area including Lake Sniardwy is a popular study site for botanical, zoological and ecological researches.

The Great Lakes area is one of the most important touristic centres in Poland, and Lake Sniardwy offers main sites for navigation and yachting (1).