The underground city of Gremdale Linkuyu is manually excavated. Early Christians were persecuted and came here to dig holes for refuge. In order to resist the invasion of a powerful empire, people have been digging on soft volcanic layers in history, and eventually created a huge underground city. It used to be a stage for the rise and fall of the world, and a hiding place for generations to escape from the troubled world. It looked desolate, but there was a lot of heaven and earth in it. This is a city without sky.