The Emperor's Palace in Milan was founded in about 291 AD by emperor Diocletian. Here Constantine and Licinius issued the Edict of Milan in 313 AD.
Residential and ambassadorial sectors, private baths and the circus, where the Emperor appeared solemnly to his subjects, and victory in chariot races became symbolic of Imperial victories, took up an entire sector of the city. The only visible traces of this vast polyfunctional quarter, which stayed in use perhaps up until the tenth century, are the remains of an ambassadorial building which had central heating; many archaeological remains are probably to be found under the buildings around Via Brisa.
The Basilica of Santa Maria in Trastevere is one of the oldest churches of Rome. The basic floor plan and wall structure of the church date back to the 340s, and much of the structure to 1140-43. The first sanctuary was built in 221 and 227 by Pope Callixtus I and later completed by Pope Julius I.
The inscription on the episcopal throne states that this is the first church in Rome dedicated to Mary, mother of Jesus, although some claim that privilege belongs to the Basilica di Santa Maria Maggiore. A Christian house-church was founded here about 220 by Pope Saint Callixtus I (217-222) on the site of the Taberna meritoria, a refuge for retired soldiers. The area was made available for Christian use by Emperor Alexander Severus when he settled a dispute between the Christians and tavern-keepers.
The church underwent two restorations in the fifth and eighth centuries and in 1140-43 it was re-erected on its old foundations under Pope Innocent II.