A complex of large areas of open water, numerous islands and long, forested, peninsula-like ridges within the Saimaa catchment area. The area is bordered to the south by Salpauselkä (an impressive glacial ridge formation), to the north-east by Puruvesi lake and to the north-west by Haukivesi lake. Nutrient input to the lake is low and consequently the vegetation on the lake is very sparse. Evidence of the slash-and-burn clearing of forests is visible in some areas, but typically forests are poor, commercially managed Pinus sylvestris monocultures. The more remote parts of the site are relatively undisturbed but human activity occurs in nearly all of the site.
Also nationally important for breeding Larus fuscus fuscus (50-80 pairs). Species of global conservation concern that do not meet IBA criteria: Crex crex (1-3 pairs, breeding).