November 17, 2009--Climber Renan Ozturk watches a local Tibetan look at an illuminated manuscript found during an August 2008 expedition to remote Himalayan caves in the ancient kingdom of Mustang, today part of Nepal.

The folio is part of a treasure trove of 15th-century Tibetan art and manuscripts that could be linked to the real-world inspiration for Shangri-La, a fictional paradise described by British writer James Hilton in his popular 1930s novel Lost Horizon.

Until recently few have been able to explore the mysterious caves--carved high into sheer cliff faces--because Upper Mustang is a restricted area of Nepal that was long closed to outsiders. Today only a thousand foreigners a year are allowed into the region.

In 2007 a team co-led by U.S. researcher and Himalaya expert Broughton Coburn and veteran mountaineer Pete Athans scaled the crumbling cliffs on a mission to explore the human-made caves. The treasures they found during that trip and the second expedition in 2008 are featured in two new documentaries, Lost Cave Temples of the Himalayas and Secrets of Shangri-La, which premiere Wednesday, November 18, on PBS (check local listings).

Read the full story and watch a preview of Secrets of Shangri-La >>

(Coburn's expedition was funded in part by the National Geographic Society, which owns National Geographic News.)

--With reporting by James Owen