Kaliningrad Oblast is the westernmost federal subject of Russia. It is a semi-exclave on the Baltic Sea within the historical Baltic region of Prussia, surrounded by Poland to the south and Lithuania to the north and east. The largest city and administrative centre is the city of Kaliningrad. The port city of Baltiysk is Russia's only port on the Baltic Sea that remains ice-free in winter. Kaliningrad Oblast had a population of roughly one million in the 2021 Russian census. It has an area of 15,125 square kilometres (5,840 sq mi).