MAXENTIUS' TEMPLE OF VENUS AND ROMA

The ruins that you see in the Forum today are the remains of Maxentius' rebuilding of the Temple of Venus and Roma. The primary difference in plan to that of the older temple is that the cellae of Maxentius' temple were apsidal and vaulted. The interior was decorated with porphyry columns, a polychrome pavement, and a deeply coved ceiling. The tiles of the roof were gilded bronze, but were removed and reused for the basilica of S. Pietro by Pope Honorius I with the permission of Heraclius in 625 CE. The temple was severely damaged, probably by an earthquake in the early 9th century, and in 847-845 Pope Leo IV built over its ruins the church of S. Maria Nova, which was itself replaced by the Church of S. Francesca Romana in 1612. You can see ruins of the apse of the cella of Venus with the church beyond it in the photo.

L. Richardson, jr., A New Topographical Dictionary of Ancient Rome (Baltimore and London 1992) 409-410.

You can compare the plans of the cellae of Hadrian's and Maxentius' temples below.

Hadrian's Temple of Venus and Roma

Maxentius' Temple of Venus and Roma

The apse of the cella of Venus is still relatively well-preserved.