A thin, hand sewn, shallow keeled raft, cobbled with long beams of bamboo, glides along, skimming the surface of a river of glass in the stillness of perpetual night. It’s nearing sunset outside, but inside Nam Lod Cave in northern Thailand, the darkness is absolute and unchanging, as it has been for millions of years.

The Thailand Coffin Caves are burial chambers, hidden at the end of long and narrow tunnels are the final resting place for hundreds of ancient humans, buried for over four centuries starting two thousand years ago in forty wood coffins.