The Zelve cirque is a delicate, horseshoe-shaped geological structure with cliffs surrounded by natural cones and arches. This fantastic site also resembles a stone "hive", with flights of steps and numerous caves dug into the rock, housing churches, dwellings and storerooms. Here and there, erosion has caused sections of the cliffs to fall away, leaving gaping holes open to the sky. This fragile, 1000 year-old troglodyte city was inhabited until 1950, when the decision was made to move the inhabitants out for reasons of safety.