Si Phan Don is the stretch of the Mekong in southern Laos where the river spreads fourteen kilometres wide and comes apart into hundreds of islands and sandbars. Then it has to leave through the biggest waterfall by volume in Southeast Asia. Khone Phapheng stopped every boat that ever tried it. That single obstacle is why there is a railway out here. The French laid a narrow-gauge line across two of the islands, reaching Don Khon in 1893 with a permanent steam service by 1897. Cargo was unloaded below the rapids, carried seven kilometres overland and floated again above the falls — and not only cargo, but whole gunboats taken to pieces for the journey. The line shut around 1940. Its concrete bridge is still standing, and what crosses it now is bicycles, on a red-dirt track that runs south past the rusting locomotive at Ban Khon.
Don Det has made an art of doing nothing. You take a hammock on a balcony over the Mekong and let the hours go with the current. In the last hour before dark you walk down to a quiet stretch of bank, where the heat eases, water buffalo come down to cool off and the boats drift home in copper light. A wooden longtail takes you through the channels that give the place its name, pulling in at deserted sandbars and palm-topped islets that empty the moment the day boats leave. On Don Khon a short walk reaches Tat Somphamit, which everyone calls Li Phi, the ghost trap. Li is a fish trap, phi a spirit of the dead, and the cataract is held to snare the spirits of the drowned so they cannot follow the river down to the villages. Boardwalks at Khone Phapheng run out above the cataracts until you can feel the ground tremble. The deep pool below them was the last refuge of the Irrawaddy dolphin in Laos, and the last of them drowned in a gillnet in February 2022.