Lake Hajka is a 4.5 km-long reservoir on the Radew river. Its waters power the historical hydroelectric power plant from 1912. Lake Hajka also serves as the compensation reservoir for the nearby hydroelectric power station in Rosnowo. It is connected to Lake Rosnowskie via Rosnowski Canal. There are tourist trails on both the northern and southern shore of the lake – the Sun Trail (Trasa Słoneczna) to the north and the Palace Trail (Szlak Pałaców) to the south.