This temple was built in imitation of the Potala in Lhasa, as Qianlong explained in an inscription on a stele in the entrance way.
Partial translation of the inscription written by Qianlong, which is given in Chinese, Mongolian, Tibetan, and Manchurian:
North of the Summer Palace lies the Potala, which was built not after the Potala on the Southern Sea, but after the Tibetan Potala. The Tibetan Potala is complete in all respects and a religious center for our vassals. In the year Keng-yin (1770) our 60th birthday fell, and, in the year Hsin-mao (1771) the 80th birthday of our august mother, the Dowager Empress. The loyal princes from Mongolia and Sinjiang, etc., and the Chiefs of the Dzungar Tribes, who had recently sworn alliance to us, gathered together to bring their good wishes. As a sign of our encouragement and friendliness to towards them we had already begun to build this temple. It was begun in the 32nd year of Ch’ien-lung [Qianlong] (1171). The labour required was great, the temple rooms are large and everything is dignified and clean in accordance with the precepts. Our vassals over the border all believe in the religion of Sakyamuni. Jehol was the spot where our grandfather the Emperor K’ang-his, pacified and appeased them, and there he granted them audiences . . . Now the temple is finished in time for a great national event that is to be celebrated by all, in a unique manner . . . In addition to this, the Torgot, who have lived in Russia for some time, have returned for religious reasons. The whole of their tribe—which numbers many ten-thousands—arrived just at this time, after wandering about for more than six months. Here is a connection that is mystic.