Explorers Charles Allen and Mark Shand, accompanied by Lama Khemsar Rimpoche and a Nepalese crew, travel to a remote and spectacular gorge in western Tibet that Allen believes is the origin of the myth of Shangri-La, the utopia envisioned by James Hilton in his novel Lost Horizon. The lost city of Shang-Shung, with its hidden ruins of monasteries, palaces, and castles, rivals Petra in Jordan and Machu Picchu in the Andes.