Located in the eastern Baltic Sea, north of Finland, East and south of Russia and Estonia. It covers an area of about 30,000 square kilometers. It is 390 kilometers east-west, 70 kilometers wide at the entrance and 130 kilometers wide at the middle. The north bank is steep and winding, with many islands; the East and south banks are low and flat. The general depth is 20-30 meters, and the deepest is at the entrance of the West end, which reaches 115 meters. There are Nirva River, Narva River and other injections. The Soima Canal opens to this bay. The freezing period is 3-5 months. Salinity is 3-6. Depth and salinity increased gradually from east to west.