Which cave art site was closed to visitors because human breath grew mould on the paintings?

Lascaux, found by four teenagers and a dog in 1940 and opened to the public after the war. By 1963 it was taking over a thousand visitors a day, and the carbon dioxide, heat and moisture they exhaled had begun growing algae on paintings that had been stable for 17,000 years. It was closed to the public in 1963 and has never really recovered.

The treatments made it worse. Antibiotics and biocides applied to kill one outbreak cleared the way for another, and black fungal stains appeared in the 2000s that were harder to remove than the green. The lesson taken at Chauvet, found in 1994, was to admit almost nobody at all - a handful of researchers for a few weeks a year, in suits, on a raised walkway.

Both now have replicas, and Lascaux's fourth version is a full facsimile of the whole cave built by artists working from laser scans. That sounds like a consolation prize and is closer to the only workable answer: the paintings survived because the cave was sealed, and the act of visiting is the thing that destroys them.