The 11 churches of Lalibela were built in the 13th century out of solid rock that sits entirely below ground level. Arranged in two main groups, the churches are connected by underground passages. In 1978, the churches became a UNESCO World Heritage site. That means the United Nations believes the site deserves special protection. Pictured here is the rock-hewn Church of St. George. (JON BRATT—GETTY IMAGES)