Europe is considered to be a continent in its own right, though some prefer to describe Europe as the vast, western peninsula of Eurasia. The generally accepted dividing line between Europe and Asia follows the Ural Mountains in Russia, the Ural River from the Ural mountains to the Caspian Sea, the Caucasus Mountains, and the Bosphorus Strait down to the Black Sea. Geographically, a great plain spreads across the whole of Europe, from Russia, westwards through Poland to the Bay of Biscay. North of this are the Scandinavian highlands, and to the south a series of mountain ranges (Caucasus, Balkans, Carpathians, Apennines, Alps, Pyrenees and Sierra Nevada). Europe can be divided into four basic climates: the northwest has mild winters and cool summers with cloud and rain throughout the year; eastern Europe has very cold winters; central Europe has cold winters and warm summers; and the region around the Mediterranean has very mild winters and hot, dry summers.