Europe is one of the seven traditional continents of the Earth. Physically and geologically, Europe is the westernmost peninsula of Eurasia, west of Asia. Europe is bounded to the north by the Arctic Ocean, to the west by the Atlantic Ocean, to the south by the Mediterranean Sea, to the southeast by the Caucasus Mountains and the Black Sea and the waterways connecting the Black Sea to the Mediterranean. To the east, Europe is generally divided from Asia by the water divide of the Ural Mountains, the Ural River, and by the Caspian Sea. Europe is the world's second-smallest continent in terms of area, covering about 10,180,000 square kilometres (3,930,000 sq mi) or 2.0% of the Earth's surface. The only continent smaller than Europe is Australia. Of Europe's 48 countries, Russia is the largest by both area and population, while the Vatican is the smallest. Europe is the third most populous continent after Asia and Afr