“Known as Mogaoku — ‘peerless caves’ — and filled with paradisiacal frescos and hand-molded clay sculptures of savior-gods and saints, they are, in size and historical breadth, like nothing else in the Chinese Buddhist world. And Mogaoku is in trouble. Thrown open to visitors in recent decades, the site has been swamped by tourists in the past few years. The caves now suffer from high levels of carbon dioxide and humidity, which are severely undermining conservation efforts.”