The Kangxi and Qianlong emperors built twelve temples here between 1713 and 1780, in Tibetan, Mongolian and Han styles, for the Mongol and Tibetan guests of the summer court. Eight of them were run by the court itself, which gave the group its name, and
外 'outer' because they lay outside the capital, beyond the Great Wall. With the Mountain Resort they became a World Heritage Site in 1994.