Basilica di Santa Sabina all'Aventino in Rome

You're standing at Santa Sabina, high up on the Aventine Hill in Rome. It's one of the best-preserved early Christian churches in the city. A priest from Illyria named Peter had it built in the fifth century. Look at the bare brick walls and the big windows. They're not glass but selenite, a translucent mineral. That's why the church still looks much as it did back in the fifth century.