Hanoi's terrain slopes from northwest to southeast, with an average altitude of about 13 meters. Affected by river alluvial deposits, about 75% of Hanoi's natural area is plains, and mountains are mainly distributed in remote suburbs. The main high mountains include Ba Vi Mountain with an altitude of 1,281 meters, Gya Mountain with an altitude of 707 meters, and Bird Foot Mountain with an altitude of 462 meters. The rivers in the territory are crisscrossed. In addition to the Red River and the Dun River, there are also the Di River, the Qiao River, the Ka Lo River, the Su Li River, the Jinniu River and other rivers. The city is dotted with lakes, and the famous lakes include the Hoan Kiem Lake, the West Lake, the Truc Bach Lake, the Seven Temples Lake, etc.