On the floor of the Baptistry, near the Gates of Paradise, two large square marble slabs inlaid with zodiacal and zoomorphic figures make a beautiful show of themselves. They are about 3 meters per side, and because both present similar features, it can be thought that were constructed together to decorate the flooring.
One of the two (let’s call it ‘marble slab #1’) has in the center a white disc with no decoration, and around it two wide rings with inlay figures. These rings are precisely divided with radial cuts that respect the figures, so that each part could be inserted correctly into the composition. And a point is very strange: in a marble slab filled with figures and motifs, the focus of the composition is entirely mute and inexpressive, without any figures.
The other slab instead (‘marble slab #2’) shows a rich series of depictions centered on the theme of the zodiac, with the image of the sun at its center surrounded by a palindrome latin verse that celebrates the star: “En giro torte sol ciclos et rotor igne.” [“I, the sun, with fire make the spheres turn as I myself turn”]. And here the strangeness is that, despite the sun being at the center of the geometries and the key of the symbolic message, its image is exactly cut in two. That attests some care taken in cutting it, which nevertheless, as was inevitable, did damage the smaller pieces of the inlay. Even so, it would have been easily avoided if they had thought from the beginning of creating a rounded panel, with the correct measurements to contain the figure of the sun, which is rather small, and the palindrome written around it. Likewise, the other cuts that we see on the marble slabs do not correspond with the patterns, which are crossed with a certain care but without any scruples.
In conclusion: if for marble slab #1 they took care in coordinating the cutting and patterns of it from its inception, for #2 it was not like that: this marble slab must have originally been all one piece and was divided only at some later point. This could be explained if there had been a relocation of the slabs: #1 could have been dismantled and easily reassembled, while with #2 this would have been problematic given its size. For that reason, they could have resorted to a very hasty solution by trying to limit the damage, but they had great difficulty in finding the incision lines that would have the least impact and be the easiest to carry out. And in fact, here in the #2 slab the incisions, which divide it into four parts, do not have radial paths like those in #1, but only linear ones, which did not involve any problems of geometry.
So why was it relocated?
I will attempt an explanation.
Originally, the Temple of Mars had a west-facing entrance that opened out onto the main road of the Roman city. When the Temple became a church, they tried to create an apse in many ways, but unsuccessfully, so in the end they decided to simply close that entrance and use instead the south door, since the other two were less suitable due to the narrow passages in the outside.
When the church became a baptistry, in 1128, it was necessary to make the east door the main entrance because it was facing the cathedral, and so a lot of work had to be done on the building. In addition, they thought of placing on that side also the beautiful floor panels that originally decorated the path to introduce visitors to the Temple. In this way they would have lent themselves very well to underscoring the importance of the new entrance of the Christian building.
Of the two panels, the one with the zodiac was evidently conceived in order to offer a key to reading the symbols of the building to those who entered it, because the space of the Temple wanted to express the destiny of glory of Rome in a heavenly and eternal projection. But what was the purpose of the other one, which offered only the view of an empty disc?
The empty disc itself helps us understand its purpose: like the porphyritic red disc near it, which was made for the emperor’s throne and is the same size, this white disc was also meant to indicate his position when he would receive, being at the entrance, the homage of the Florentines who were crowding the piazza in front of it.
But that is not everything, because one must consider that in 1128 the altar must certainly have been there already, given that the building had long since became a church, and it was placed on a presbytery raised by a few steps more or less as we see now. Therefore, it being inconceivable that the altar and presbytery were demolished to bring back in light the panels on the underlying floor, one must conclude that those panels had already been moved from their original placement and put away somewhere. What happened to these marbles must have been the same that happened to the marbles of the lantern and to the column of the statue of Mars: when, in the fifth century, the Temple became a church, all of the prized marble was dismantled and stored nearby, to then be reused if the occasion presented itself.
This happened in 1128 for the panels, and it was probably then that they were fractured.
Above: diagram of the incisions (in red) of marble slab #1
Below: diagram of the incisions (in red) and of the fractures (in blue) of marble slab #2
Detail of the sun at the center of the slab with the zodiac. The incision damaged the inlays in the central part of the solar crown.