Estonian Peipsi Järv
Lake, north-central Europe, forming the boundary between Estonia and Russia.
Lake Peipsi is 60 mi (97 km) long and 31 mi (50 km) wide, and it is frozen for half of the year. In 1242 the Russians, under Alexander Nevsky , defeated the Teutonic Knights (see Teutonic Order ) on the frozen lake in the "Battle on the Ice," forcing the order to relinquish claims to Russian lands.