The colossal Buddhist statues in the cliffside caves outside this northern Chinese city, carved from golden sandstone by Turkic-speaking nomad conquerors in the fifth and sixth centuries, were so covered in coal dust that when visitors blew on them, black clouds rose up.

Called the Yungang Grottoes, the relics had survived the rise and fall of dynasties, modern wars and the Cultural Revolution. But the scourge of a more prosperous China — industrial pollution — had been eating away at the sandstone.

Chinese officials and preservationists have embarked on an ambitious effort to protect them that could become a model for saving antiquities at other sites. They have not only cleaned the statues here and created a vast park, but also shut down nearby coal mines and removed or regulated other sources of air pollution.