Si Phan Don

Known in English as the Four Thousand Islands, Si Phan Don is an archipelago formed where the Mekong River broadens dramatically near the Cambodian border in southern Laos, creating a maze of channels, sandbanks, and islands of varying size. The largest permanent islands — Don Khong, Don Det, and Don Khon — are inhabited and connected by French-era railway infrastructure originally built to bypass the Khon Phapheng and Somphamit rapids, the widest waterfalls by volume in Southeast Asia. Critically endangered Irrawaddy dolphins congregate in the deep pools between Don Det and the Cambodian border.