Tham Lot is one of the largest and most impressive cave systems in Thailand — a 1,666-metre river cave that the Nam Lang stream flows through before disappearing underground. The cave has three main chambers of cathedral proportions, filled with stalactites, stalagmites, and ancient teak coffins left by the region's prehistoric inhabitants. Guides with kerosene lanterns lead visitors through the cave, which is partially navigated by bamboo raft on the stream.
The archaeological significance of Tham Lot is considerable. The wooden log coffins found inside date back over 2,000 years and are the remains of a burial culture about which little is known. Some of the coffins are still visible on natural ledges high in the cave walls. The guide service at the cave entrance is well-organized, with mandatory guides required for all visits — this is partly for conservation reasons and partly because the cave is genuinely easy to get lost in without a light. Plan for a visit of at least two to three hours. The cave itself closes at 5pm, though the bat and swift exchange at the entrance happens right around dusk, outside the cave proper.