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:The Pilgrimage Church of Wies (Wieskirche) is an oval rococo church, designed in the late 1740s by Dominikus Zimmermann. It is located in the foothills of the Alps in the municipality of Steingaden.
The sanctuary of Wies is a pilgrimage church extraordinarily well-preserved in the beautiful setting of an Alpine valley, and is a perfect masterpiece of Rococo art and creative genius, as well as an exceptional testimony to a civilization that has disappeared.
The hamlet of Wies, in 1738, is said to have been the setting of a miracle in which tears were seen on a simple wooden figure of Christ mounted on a column that was no longer venerated by the Premonstratensian monks of the Abbey. A wooden chapel constructed in the fields housed the miraculous statue for some time. However, pilgrims from Germany, Austria, Bohemia, and even Italy became so numerous that the Abbot of the Premonstratensians of Steingaden decided to construct a splendid sanctuary.