Phoksundo Lake at 3,612 m is the deepest lake in Nepal, at approximately 145 m depth, and one of the most strikingly coloured: the water is turquoise-blue, fed by glacial streams and with no outflow river, which accounts for the unusual clarity. The lake sits inside Shey Phoksundo National Park, Nepal's largest national park at 3,555 sq km. A full rest day at Phoksundo (D13) allows time to walk the lake shore, visit Ringmo village above the lake and observe the Bon monastery there.
Dolpo, and specifically the villages of Dho Tarap and the Phoksundo area, are among the last intact communities following the Bon religion, which pre-dates Tibetan Buddhism, alongside a culture that is Tibetan in language, dress and architecture. Flat-roofed stone houses, chortens, mani walls and prayer flags mark the villages, and the local calendar follows the Tibetan agricultural and festival system. The 1999 film 'Himalaya' (also released as 'Caravan') by Eric Valli was set in the Dolpo community and brought the region to wider international attention.