The Cathedral Excavations Museum, located beneath Residenzplatz and Domplatz, gives visitors a fascinating view of building work since the Roman Age in the area of today’s cathedral.

Particularly impressive are the excavation finds of a Roman villa built in the late second/early third century over the remains of an older house and aligned with a road passing to the south. Visitors can see extensive parts of the former central residential area, a columned interior courtyard, corridors, and rooms with drainage and warm air-heating systems. There are mosaic floors of outstanding quality, in part superimposed one above the other in two layers.