Wat Phou is a ruined Khmer Hindu temple complex in southern Laos, located at the base of Phou Khao mountain, about 6 km from the Mekong in Champasak Province. According to scientists, Wat Phou is the oldest temple in Laos, dating from the 5th century, once the center of Hinduism, worshiping the god Shiva. By the 13th century, Wat Phou became the center of Theravada Buddhism, which exists to this day, and became one of the places to keep the values of Lao history and culture. In 2001, Wat Phou was recognized by UNESCO as a World Heritage Site.
The Wat Phu festival is held annually, continuously for 3 days on the full moon day of the third lunar month (January to February) and coincides with the Makha Busa Buddhist Festival. Devotees throughout Laos and neighboring provinces in northeastern Thailand and Cambodia eagerly pilgrimage here. This is also the opportunity for surrounding plain and mountain populations to meet each other, maintaining these relations.
Noong Vieng Lake (the lake of the citadel) in front of the ancient temple is the center of the festival. Processions, recitals, and chants take place during the three days festival. Boats racing (dugouts), game “catch-ducks”; volleyball and petanque competitions are also organized. Sometimes, elephant procession, buffalo and cock fights, and dances are also shown.
According to Wikipedia, luangprabang-laos.com and sonasia-holiday.com