Church of Santa Costanza
Upon first glance, one would notice that this structure is round, rather than rectangular, as is thought when a church is pictured. The church is built in a group of circular rooms, which in turn are all circling one central room, likely the sanctuary. ... Judging from the plan of the church, the room was only a dome on the inside, and had a triangular roof on the outside. ... Exploring more details of the central room, there is a large altar in the center, made of the same stone as the rest of the church.