The geology of Russia, the world's largest country, which extends over much of northern Eurasia, consists of several stable cratons and sedimentary platforms bounded by orogenic (mountain) belts. The European part of Russia is on the East European craton, at the heart of which is a complex of igneous and metamorphic rocks dating back to the Precambrian. The craton is bounded on the east by the long tract of compressed and highly deformed rock that constitutes the Ural orogen. The area between the Ural Mountains and the Yenisei River is the young West Siberian Plain. East of the Yenisei River is the ancient Central Siberian Plateau, extending to the Lena River.