- Janet DeLaine
A temple in the *Campus Martius dedicated to all the gods. The first Pantheon, built by M. *Vipsanius Agrippa in 27–25 bce, was rebuilt first under Domitian, and again late in the reign of Trajan in its current form. Completed probably by Hadrian, it retained Agrippa's name in the dedicatory inscription (CIL 6. 896); it was later repaired by *Septimius Severus and *Caracalla. The building was entered from a long rectangular forecourt through a traditional octastyle Corinthian portico (33.1×13.6 m. (109×45 ft.)) of red and grey granite columns, 48 Roman feet (11.8 m.) high, although the original design may have been for 60 (Roman) ft. columns. A rectangular block links this to the circular cella, 43.3 m. (142 ft.) in both diameter and height, lit from a single central oculus, 9 m. (30 ft.) in diameter. The cylindrical wall of the brick-faced concrete rotunda (6.2 m. (20 ft.) thick) supporting the dome is divided into eight piers by the doorway and alternating semi-circular and rectangular recesses at the lower level with internal key-shaped chambers above, all linked by a complex series of relieving arches extending to the haunches of the dome. The six lateral recesses were divided off by marble columnar screens crowned by a continuous entablature while small aedicules framing statue niches decorated the piers between them. Richly coloured marble veneer, substantially preserved in the lower zone, decorated the interior; a small section of the attic decoration has been restored to its original form. The great bronze doors are ancient. The play of light from the oculus across the vast surface of the richly coffered dome is largely responsible for the building's enduring fascination.