The Tonle Sap Lake is the largest fresh water lake of Cambodia. There are two extraordinary features of the river which forms the lake. Firstly the direction of water changes twice a year and secondly the lake increases and decreases with seasons. The lake is small during the year measuring around one meter deep stretched at an area of 2700 square km. Usually the water of Tonle Sap River connects the lake with the Mekong River but it happens the opposite during monsoons. The water starts moving upwards increasing the area of the lake to 16000 sq km and depth to 9 meters.