The floor of the Octagon was made of large colored marbles slabs and tiles organized in panels symmetrically distributed vis-à-vis a central axis. It belongs to the category of floors made using the opus sectile technique, combining characteristics of the type of opus sectile with a large radius, opus sectile with a medium-sized square radius with simple motifs, and opus sectile with a small radius of geometric type with simple elements as described by the Italian scholar F. Guidobaldi for floors of the same historical period in the area of Rome.
From the marble pavement, which in antiquity covered an area of 700 square meters, 250 meters survive in fragments, preserved chiefly in the northeast part of the building, which survives in better condition vis-à-vis the west part. Parts of the floor are also preserved in front of and inside the niches, while only the mortar substrate remains preserved in the central section of the building.
