Tonlé Sap is Southeast Asia's largest freshwater lake and the hydrological heart of Cambodia. It sits about 15 kilometres south of Siem Reap at its nearest point, and the floating and stilt villages along its shores are one of the most vivid experiences the Siem Reap region offers. The lake's seasonal flood-drain cycle is extreme: from a modest reservoir in the dry season it swells to an inland sea that covers an area roughly the size of Switzerland in the wet season, inundating forests that remain submerged for months.
The floating villages of Chong Kneas (the most accessible, 15km from town), Kampong Phluk, and Kampong Khleang (the largest and most authentically un-touristified) give very different experiences. Chong Kneas is crowded and somewhat exploitative of visitors; Kampong Phluk, with its stilt houses rising seven metres above the dry-season mud, is more atmospheric; Kampong Khleang requires more effort but rewards it. A boat trip of two to three hours takes in the village life, the fishermen, and in the wet season the extraordinary sight of trees standing in metres of water. Sunset from the lake is spectacular.