THE VOLCANIC landscape of Cappadocia, in central Turkey, has eroded over millennia to form mountain ridges, sandstone valleys, and rows of Gaudiesque cones that the tourism industry likes to call fairy chimneys. Over 4,000 years, humans, too, have carved the porous rock, excavating a warren of caves, tunnels, and passages. Among 205,000 acres of archaeological sites in the region, there are dozens of abandoned underground cities. One, Kaymaklı, is over 4,000 years old and extends eight stories belowground, complete with stables and wine cellars. Another, Derinkuyu, was vast enough to have housed 20,000 people at once.
While these larger archaeological treasures haven’t been occupied in more than a hundred years, many of the individual homes carved into the area’s rocks are still in use. Oktay, 72, and Hanife Torun, 64,…