A small group of artists, carrying engraving tools, torches, and other supplies, assembled at the base of the towering limestone outcrop, near the mouth of a dark cave. Together, they entered the lightless space. For 40 minutes they wormed through passages and scrambled over speleothems. Their juniper-branch torches cast a warm, flickering light and shed bits of charcoal like bread crumbs along the trail. Nearly a quarter-mile from the cave entrance, they reached their canvas: a rugged limestone wall, 40 feet long and eight feet above the cave floor. They…
