Terracina Cathedral — officially the Concattedrale dei Santi Cesareo e Pietro — stands on the main piazza of the upper town, and like much of Terracina, it is built directly on top of ancient Roman remains. The medieval church was constructed over the former Capitolium, the pagan temple that would have dominated the Roman forum. You can see the exposed stonework of the forum beneath and beside the piazza itself.
The cathedral's facade incorporates a portico of ancient Roman columns, giving the building a hybrid appearance that is characteristic of the way medieval Italian towns cannibalized their ancient predecessors. The interior is plain but has some notable Cosmatesque mosaic work. The whole arrangement — cathedral, ancient columns, Roman forum remains, and a functioning town square — is a compact lesson in how Italy layers its history.