Yün-kang caves 

A site in north China near the ancient capital city of Ta-t'ung (modern Shansi Province) where a number of images were carved in rock representing Buddhas and Bodhisattvas. Work began shortly after 460, as part of a revitalization of Buddhism after the persecution in North China of 446. Work continued even after the Northern Wei rulers moved the capital to Lo-yang in 493.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)