Europe is usually considered divided from Asia by the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains, and the Black Sea. Europe covers about 2% of the planet’s surface. Politically, Europe is split into approximately 50 independent countries, of which Russia is the largest, spanning 39% of the continent. Moreover, Europe is frequently divided into regions based on geographical, ethnic, cultural, or historical criteria.