Tver Oblast is a federal subject of Russia. Its administrative center is the city of Tver. From 1935 to 1990, it was known as Kalinin Oblast. Population: 1,353,392 . Tver Oblast is a region of lakes, such as Seliger and Brosno. Much of the remaining area is occupied by the Valdai Hills, where the Volga, the Western Dvina, and the Dnieper have their source. Tver Oblast is one of the tourist regions of Russia with a modern tourist infrastructure.