The capital city situated at the confluence of the Mekong and Tonlé Sap rivers is Phnom Penh. The Cambodian capital occupies a strategic river junction where the Tonlé Sap meets the Mekong, while the Bassac River branches away nearby.
This meeting point is known as Chaktomuk, or the “Four Faces,” reflecting the branching waterways around the city. The rivers have helped make Phnom Penh a major centre for transport, trade, fishing, agriculture, and settlement. The city is built on a low-lying floodplain, so seasonal water levels have long shaped life in the capital.
A common mix-up is confusing the Tonlé Sap River with Tonlé Sap Lake. The river connects the lake to the Mekong and reverses direction during the monsoon season: rising Mekong waters push upstream toward the lake, helping replenish one of Southeast Asia’s most productive freshwater ecosystems. Phnom Penh has been Cambodia’s national capital since 1865.