Europe's most significant feature is the dichotomy between highland and mountainous Southern Europe and a vast, partially underwater, northern plain ranging from the British Isles in the west to Poland in the east. These two halves are separated by the mountain chains of Pyrenees, Alps, Carpathian and Balkan Mountains. The northern plains are delimited in the west by the Scandinavian mountains. Major shallow water bodies submerging parts of the northern plains are the Celtic Sea, the North Sea, the Baltic Sea complex, and the Barents Sea.