The Mekong is one of the great rivers of Asia, the twelfth longest in the world and sixth in terms of discharge. It rises from the Qinghai-Tibetan Plateau in China, and flows through Laos, Thailand and Cambodia on its way to its delta in Vietnam. In northern Cambodia, the river enters a fluviatile lowland landscape with broad floodplains and extensive backwater swamps, many of which remain flooded throughout the dry season. The Great Lake and Tonle Sap River, in central Cambodia, form an integral part ofthe Mekong floodplain system. The Great Lake is the largest lake in Southeast Asia and lies in a vast shallow basin to the west of the Mekong, and is surrounded by a broad belt of freshwater swamp forest.