The most famous work of art in the cathedral is considered to be its unique inlaid marble mosaic floor - one of the most ornate in Italy, covering the whole floor of the cathedral. This undertaking went on from the 14th to the 16th centuries, and about forty artists made their contribution. The floor of the cathedral is divided into 56 panels of various sizes and shapes with images of biblical scenes, sibyls, and allegorical figures.
The first of the existing images date back to around 1370.