The remains you see here were part of the Basilica of St. Euphemius built in 1031 by Litigerius, bishop of Como. It was demolished by the city of Como in 1169 (historical sources document the deed of foundation). Archaeological excavation has revealed the existence of an earlier religious building, erected during the Early Christian period or the Early Middle Ages. The earliest ruins date back to Roman times.
The Romanesque building was a large three-aisled basilica (22×62 m); the aisles, separated by octagonal masonry columns, terminated in three semicircular apses facing east. A central staircase of 9 steps allowed visitors to ascend to the raised presbytery while in the wings two smaller staircases led down to the crypt. Given the composition of the terrain (for the most part bedrock), the right apse was placed at the same level as the aisles while the left apse was built on a somewhat higher level.References:
Built around AD 90 to entertain the legionaries stationed at the fort of Caerleon (Isca), the impressive amphitheatre was the Roman equivalent of today’s multiplex cinema. Wooden benches provided seating for up to 6,000 spectators, who would gather to watch bloodthirsty displays featuring gladiatorial combat and exotic wild animals.
Long after the Romans left, the amphitheatre took on a new life in Arthurian legend. Geoffrey of Monmouth, the somewhat imaginative 12th-century scholar, wrote in his History of the Kings of Britain that Arthur was crowned in Caerleon and that the ruined amphitheatre was actually the remains of King Arthur’s Round Table.
Today it is the most complete Roman amphitheatre in Britain.