In June 1900, self-appointed Taoist caretaker Wang Yuanlu was clearing sand from a cave complex near Dunhuang, China, when the smoke from his cigarette drifted sideways toward a plastered wall. Behind it he found Cave 17, the library cave, packed floor to ceiling with more than 50,000 items dating from 406 to 1002 CE. The Mogao Caves, nearly 500 temples on the Silk Road, trace back to 366 CE, when the monk Lezun saw a vision of a thousand Buddhas in golden light and carved a meditation cell, soon joined by the monk Faliang. Donors from women’s groups to merchants to emperors funded the caves, and in 695 CE, after an edict from Empress Wu Zetian, a 35.5 meter Maitreya Buddha rose inside a multi-story pavilion.

The caves escaped Emperor Wuzong’s 845 CE persecution of Buddhism because Dunhuang was then under Tibetan occupation. The library was sealed sometime after 1002, possibly as a waste store, possibly in fear of the Karakhanids and the Xixia, or possibly as a time capsule for a prophesied age of decline. After 1900 came the explorers: Aurel Stein bought 13,000 items in 1907 for about 130 pounds, Paul Pelliot spent three weeks reading by candle in 1908 and took about 10,000 for 90 pounds, White Russian soldiers blackened murals in 1921, and Langdon Warner stripped murals off walls in 1924.

• The Diamond Sutra of 868 CE, the earliest known dated printed book, found alongside Nestorian Christian texts, Hebrew prayers, and manuals for Go
• Why sculptors built giant statues from clay over wooden armatures and reed bundles instead of carving the crumbly gravel cliff
• How lead-based shading pigments oxidized black over a thousand years, and why the Dunhuang Academy preserves them as they are
• Painter Zhang Daqian’s copies of the murals in the 1940s and Premier Zhou Enlai sending troops to protect the site during the Cultural Revolution
• How visitors’ breath damages the paint, and the digital twin project that lets people explore the caves in virtual reality