Backed by fuzzy green hills, the gigantic lake wrapped almost entirely around Sangkhlaburi was formed in the 1980s by the Vajiralongkorn Dam. Two of the villages submerged under the new lake were moved up to their present location; Saphan Mon was built to connect them. About all that remains now are ruined buildings from three temples. A boat ride allows you to see them up close, as well as feel the pace of life on the lake.
The nearest temple, just visible from the bridge, is Wat Wang Wiwekaram Gao (gao means old); this was the site of the Mon village. When the lake rises to its highest point, only the very top of the ubosot (chapel) and bell tower stay dry. Nearby, Wat Si Suwannaram Gao was the temple in the Thai-Karen village. It emerges when the lake is very low, while Wat Somdet Gao sits in the forest high on a hill and stays dry year-round. The new Wat Somdet is along the road into town.