 The early Christian church, built on the remains of three Roman villas still visible beneath the monastery, was situated immediately outside the wall of the Baths built by Diocletian and the Servian Wall, the first walls built to defend the city.According to tradition, the Church was erected on Susanna's House, where the same Saint was martyred.In the 4th century it was marked with the designation "ad duas domos" (at the two houses).