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13 of the most bizarre lakes in the world

Tonlé Sap

Photo: Jialiang Gao/Wiki Commons/GNU

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Tonlé Sap

The unique ecosystem of Cambodia's Tonlé Sap evades classification as either a lake or a river.

During the dry season, the waters of the Tonlé Sap drain into the Mekong River, but during the monsoon season the flow of water is so massive that it actually pushes back up from the Mekong, forming the largest freshwater lake in Southeast Asia. This lake is particularly unusual for the fact that its flow violently changes direction twice a year.

Because of these bizarre conditions, the region is a treasure trove for biodiversity and it has been designated a UNESCO biosphere.