Around 600 A.D. monks in the Cloud Dwelling Monastery (Yunjusi) in the mountains south of Beijing began carving the Buddhist canon into stone. When engraving was finished around 1200 A.D, nearly thirty million characters had been carved on fifteen thousand stone slabs. Because the monks believed the end of the world was near, the stones were hidden in an underground pit within the temple compound and in mountain caves around the Thunder Sound Cave, (Leiyindong) to await the next world age.