Tver Oblast (Russian: Тверска́я о́бласть, Tverskaya oblast) is a federal subject of Russia (an oblast). Its administrative center is the city of Tver. From 1935 to 1990, it was known as Kalinin Oblast (Кали́нинская о́бласть), named after Mikhail Kalinin. Population: 1,353,392 (2010 Census).Tver Oblast is a region of lakes, such as Seliger and Brosno.