Champasak is a province in the southwest of Laos, near the border with Thailand and Cambodia. It is one of the three principalities that succeeded the Lan Xang kingdom. The Mekong River flows through the province. The capital of the province is Pakxe, which takes its name from Champasak, the former capital of the Champasak Kingdom. It has 15,415 km² of surface. The small town of Champasak, where the Khmer ruins of Wat Phu are located, is the capital of the homonymous district. The Khone Phapheng falls are located in the province. Champasak can be reached from Thailand by the Chong Mek border crossing at Vang Tao, where the road leads east towards the town of Pakxe.