Wat Phou was a part of the Khmer empire, centred on Angkor to the southwest, at least as early as the reign of Yashovarman I in the early 10th century. Later, the original buildings were replaced, but some of the original stone blocks were reused. The temple as it stands today was built primarily during the Koh Ker and Baphuon periods of the 11th century. Minor changes were made during the following two centuries, before the temple, like most in the empire, was converted to Theravada Buddhist use. This continued after the area came under control of the Lao, and a festival is held on the site each February. Little restoration work has been done, other than the restoration of boundary posts along the path. Wat Phou was designated a World Heritage Site in 2001.