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:Rosenborg Palace was built in the period 1606-34 as Christian IV’s summerhouse just outside the ramparts of Copenhagen. Christian IV was very fond of the palace and often stayed at the castle when he resided in Copenhagen, and it was here that he died in 1648. After his death, the palace passed to his son King Frederik III, who together with his queen, Sophie Amalie, carried out several types of modernisation.
The last king who used the place as a residence was Frederik IV, and around 1720, Rosenborg was abandoned in favor of Frederiksborg Palace.Through the 1700s, considerable art treasures were collected at Rosenborg Castle, among other things items from the estates of deceased royalty and from Christiansborg after the fire there in 1794.
Soon the idea of a museum arose, and that was realised in 1833, which is The Royal Danish Collection’s official year of establishment.