The Mogao Caves, carved into cliffs near the town of Dunhuang in northwest China, date from the 4th to the 14th century AD and lay along the ancient trade route known as the Silk Road. There are about 500 of them, and when they were discovered in the early 20th century, they held tens of thousands of manuscripts and scrolls, and thousands of sculptures and wall paintings.
This photo was taken by James Lo in the 1940s; the sculpture represents the Buddha achieving parinirvana—the nirvana-after-death that occurs when a person dies after attaining nirvana during their life, ending the cycle of death and rebirth. It dates from the Middle Tang dynasty (781–848). See more here.