The Church of St. George, Lalibela, EthiopiaExcavated from solid rock in the twelfth century, the churches of Lalibela were distinctive Christian structures, invisible from a distance and apparent only when looking down on them from ground level. Local legend has it that their construction was aided by angels. This one in the shape of a cross is named for Saint George, the patron saint of Ethiopia.(© Gavin Hellier/Robert Harding World Imagery/Corbis)