Set between two porphyry columns that support a reused marble architrave are the original bronze doors of the Temple of Divine Romulus, deified by his father Maxentius in AD 309, when the boy is presumed to have died. They open into a rotunda fifty Roman feet in diameter covered by a cupola, which now is accessible from the rear through the Basilica of Santi Cosma e Damiano. Early in the sixth century, the temple was converted into a vestibule for the church, which also occupied the southwest corner of the Temple of Peace, the first buildings in the forums to be Christianized.
A better perspective is from the Palatine Hill, where one can see the remnants of the concave façade flanking the doors, with niches for statues. On either side, two long apsidal halls opened directly onto the Via Sacra, which has settled and now is much lower than it was in the fourth century. The doors to these halls were flanked by columns set on high plinths, and projected forward of the curved front of the rotunda, which can better be imagined in the map below. Two of these columns, taken from another building (as was much of the façade), are still in place. Only the plinths of the others remain.
Originally, the vestibule connected with the much larger rectangular hall set off obliquely behind and, through it, with the Temple of Peace. It is the back wall of this building, in fact, that held the marble plan of Rome (Forma Urbis Romae).
See also Forma Urbis Romae.
