The most impressive, and yet least-visited cave in Khammuan, is the amazing Tham Lot Se Bang Fai. Located at the edge of Hin Namno NPA, the cave is the result of Se Bang Fai river plunging 6.5km through a limestone mountain, leaving an underground trail of immense caverns, impressive rock formations, rapids and waterfalls that have been seen by only a handful of foreign visitors.
The cave wasn't professionally mapped until 2006, and the Canadian/American that led the expedition concluded that Tham Lot Se Bang Fai is among the largest river caves in the world. Traversing the entire cave involves eight portages and is only possible during the dry season, from January to March. Local wooden canoes can only go as far as the first portage, about 1km into the cave, making inflatable rafts or kayaks the only practical option for traversing the entire length of the cave.
The base for visiting the cave is Ban Nong Ping, a mixed Lao Loum/Salang village about 2km downstream from the cave entrance. However homestays are currently unavailable due to recent scams demanding travellers pay exorbitant rates for a goat to be slaughtered to appease the cave's spirits. With a month's warning you can organize a trip here with Green Discovery but the privilege will cost you a princely US$800. By the end of 2013, assures Tha Khaek's Tourist Information Centre, homestays will resume, as will organized treks out of their office.
