Lake Peipus
In January 1945, some territories of Estonian SSR were ceded to the Russian SFSR: the Russian–Estonian boundary in the north of Lake Peipus was moved westwards by about 12 kilometers from its interwar location (which was delimited by the Treaty of Tartu); the new boundary (which exists up until these days) runs along Narva river. The Russian-Estonian boundary that used to run in the middle of Lake Peipus did not change, while the boundary south of Lake Peipus was also moved westwards (by about 25 kilometers). Overall, about 2000 km2 of land changed hands, including Ivangorod ("Jaanilinn", then eastern suburb of Narva), the town of Pechory ("Petseri"), and areas in and around Izborsk ("Irboska"), Lavry ("Laura"), and Rotovo ("Roodva"), and the Kolpina Island ("Kulkna") in southern Lake Peipus.