Osveiski is a large complex of lakes, forests, and transition and bog mires on the border with Latvia and the Russian Federation. The boundaries of the Site were realigned in 2016 with those of the Landscape Reserve, leading to an increase of nearly 8,000 hectares. The core of the site is Lake Osveiskoe, the biggest eutrophic lake in Belarus, which is rapidly overgrowing with aquatic vegetation but still plays an important role in the hydrological and climatic regime of northern Belarus. The Site regularly hosts more than 10,000 migrating waterbirds and provides important breeding grounds for the willow grouseLagopus lagopus, the Eurasian bittern Botaurus stellaris and the Eurasian curlew Numenius arquata. It regularly supports over 1% of the biogeographic population of the common crane Grus grus and the bean goose Anser fabalis rossicus. Human uses include logging, cattle grazing, the collection of berries, mushrooms and medicinal plants, fishing, and hunting. Four tourist routes are located within the Site. The main threats relate to drainage, dams and water management, as well as fishing and the harvesting of aquatic resources. After degradation of the lake’s ecosystem caused the number of migrating waterbirds to fall, a management plan and a restoration plan were put in place. Work to restore the hydrological regime of mires and repeated waterlogging of degraded peatlands have stabilized the water levels of the mires and the lake.