Siberia is an extensive geographical region spanning much of Eurasia and North Asia. Siberia has historically been a part of modern Russia since the 17th century. The territory of Siberia extends eastwards from the Ural Mountains to the watershed between the Pacific and Arctic drainage basins. The Yenisei River conditionally divides Siberia into two parts, Western and Eastern. Siberia stretches southwards from the Arctic Ocean to the hills of north-central Kazakhstan and to the national borders of Mongolia and China.