Attapeu Province
Nong Fa Lake or Nongphatom Lake ('Blue Lake') is a volcanic crater lake in the mountains of Sanxay District, Attapeu Province, southeastern Laos, in the Dong Ampham National Biodiversity Conservation Area, about 12 kilometres from the Vietnamese border. At an elevation of 1154 metres, the maximum depth of the lake is reportedly 78 metres, although locals have claimed that the depth is unknown, having attempted fruitlessly to gauge the depth with bamboo poles.