MAXENTIUS VERSUS CONSTANTINE?

After the construction of the rotunda and of its side halls, the rectilinear façade and the rectilinear step rings on the rear side offered little resistance to the outward thrust of the dome, which was buttressed by two walls – the concave façade built against the original rectilinear one – that were placed on either side of the main entrance. The dome's outward thrust was directed toward the corners of the side halls. In addition, the four windows in the rotunda's drum were blocked, also because of the building's instability. Inevitably, these alterations had serious repercussions. I argue that the changes introduced in this new phase were the direct result of larger decisions affecting the building as a whole, and no doubt a new architect was forced to put his hand to the entire design. On the rear side of the rotunda – between the dome and the original façade of the great hall – the tripartite window opened below the Severan arch was walled up, and eventually a gabled structure, originally covered with tiles of white marble, was built between the window's infill and the rectilinear step rings on the dome's rear side. As for the great hall, not only its façade toward the Via Sacra but also its other walls were raised (after the removal of the original roof, of course). To close the rear side of the great hall, a huge arch was built precisely where the hall became narrower and, finally, the present semicircular apse was added, covered by a thin semidome of terra-cotta tubes. The remodeling of the great hall can be associated with an architectural practice that is quite different from that of the rotunda. The differences in building techniques cannot be explained with the involvement of two or more contractors within the same project; indeed, the apse and its vault came at the end of a sequence of building phases that are reconstructed in the next pages for the very first time.