A Roman house in the upper part of the town, with mosaic pavements, probably belonged to Vespasia Polla, the mother of the emperor Vespasian.
Glass was largely used in pavements, and in thin plates as a coating for walls.
The same character of elaborate decoration, guided almost uniformly by good taste and artistic feeling, is displayed in the mosaic pavements, which in all but the humbler class of houses frequently form the ornament of their floors.
Imitations of porphyry, of serpentine, and of granite are also met with, but these were used chiefly in pavements, and for the decoration of walls, for which purposes the onyx-glass was likewise employed.
In 1884-86 portions of a number of fine mosaic pavements were discovered extending over a very large area under the cloister and other parts of the cathedral, about 7 ft.