Carved out of the western cliffs of the Mingshashan Mountains, the Mogao Grottoes consist of a sprawling complex of 492 caves and grottoes, which reflect centuries of evolving Buddhist philosophy and art in China. Created over the course of a millennia starting in the fourth century AD and used for meditation, worship and the storage of sacred texts, these temple caves contained tens of thousands of frescoes, paintings, sculptures and terracotta statues. They also housed innumerable manuscripts, most notably the Diamond Sutra, which was produced in 868 AD making it the earliest dated and printed book yet found. Surrounded by desert, people pray to these grottoes for luck, given their dangerous lives in the desert. Discovered in the early 20th century, the Mogao Grottoes were named a UNESCO World Heritage Site in 1987.