Lake Peipsi (Estonian: Peipsi järv, Russian: Chudskoe ozero, German: Peipus-See) is a large lake, on the border between Estonia and Russia in Eastern Europe.

It is the fourth largest lake in Europe, after Lake Ladoga and Lake Onega in Russia north of St. Petersburg, and Lake Vänern in Sweden, followed by Lake Saimaa and Lake Inari in Finland.

It covers 3,500 square kilometers, and has an average depth of 7m, the deepest point being 15m. The lake is used for fishing and recreation, but suffers from severe environmental damages.

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