Reminder that the world's (second) oldest Christian country is not in the Middle East or Europe. It's Ethiopia. There are monolithic churches there that were not "built," but carved directly into the rock. In 1187, Jerusalem was captured by Muslims led by Saladin, making pilgrimages to the Holy Land impossible. The Ethiopian Church was cut off from the rest of Christendom. So, King Lalibela built a "new Jerusalem" in Ethiopia, instructed in a vision to build a heavenly kingdom. He carved 11 rock churches straight down into the volcanic rock. Interiors were hollowed out in a series of decorative vaults and columns. The cruciform Church of St. George (below) is the best known. It is 30 meters tall, and some 4,000 cubic meters of rock were excavated to make it. Following ancient tradition that the Ark of the Covenant still resides in Ethiopia, a replica of it is kept within the church...