The vast lowland plains that dominate the Russian landscape carry some of the world’s longest rivers, like the Caspian Sea, Lake Onega, Lake Lena, Lake Brosno, and others. Russia contains an enormous number of lakes. Lake Ladoga in Northern Russia is the largest lake in Europe. Lake Baikal in southeastern Siberia is the largest body of fresh water in the world and it is the oldest lake in the world, an estimated 25-30 million years old. The water Lake Baikal holds makes up 20% of the fresh surface water in the world.