The temple of Jupiter dominates the Forum, and more than any other structure gives it character. As we have seen, its orientation accords with that of the colonnade of Popidius. It probably dates from the pre-Roman period, the columns being of tufa covered with white stucco. The earthquake of the year 63 left the temple in ruins, and at the time of the eruption the work of rebuilding had not yet commenced. In the meantime, it was used as a workshop for stonecutters. The journal of the excavations reports the finding here of the torso of a colossal statue out of which a smaller statue was being carved. A place for the worship of the divinities of the temple must temporarily have been provided elsewhere.
The temple stands on a podium 10 Roman feet high, and including the steps, 125 Roman feet long ([Fig. 18]). Very nearly a half of the whole length is given to the cella; of the other half, a little more than two thirds is occupied by the portico, leaving about a third (20 Roman feet) for the steps. The pediment was sustained by six Corinthian columns about 28 feet high. This arrangement—a deep portico in front of the cella—is Etruscan, though the canon of Vitruvius, that in Etruscan temples the depth of the portico should equal that of the cella, is violated. The high podium also, with steps in front, is characteristic of Etruscan, or at least of early Italic religious architecture. On the other hand, the architectural forms of the superstructure are Greek, and these in turn have had their influence upon the plan; the intercolumniations are not wide, as in the Tuscan style with its wooden architrave, but narrower, as in the Greek orders. Vitruvius speaks of temples such as this, in which Greek and Etruscan elements are united, at the end of his directions for the building of temples; they are a development of Roman architecture.
The arrangement of the steps is peculiar. Above is a series of long steps reaching nearly across the front ([Fig. 19]); below are two narrow flights near the sides, and between them is the projecting front of the podium, used as a tribune, which has already been mentioned ([p. 48]).
Fig. 19.—Ruins of the temple of Jupiter.
That an altar stood at the middle of this platform is proved by a relief with a representation of the north side of the Forum, found on the base of a chapel of the Lares in the house of the wealthy Pompeian, L. Caecilius Jucundus. At the left we see the arch near the façade and a strip of wall connecting it with the temple; next a corner of the platform with an equestrian statue; then a flight of steps, and the front of the platform with an altar at the middle; finally the other flight of steps and another equestrian statue in a position corresponding with that of the first. The columns shown in the relief do not agree in number or style with those of the façade of the temple, but such inaccuracies are common in ancient representations of buildings, and there can be no doubt that the temple of Jupiter is represented; the relief has, in fact, been used in making our restoration of the arch at the left ([Fig. 13]).
Both the portico and the cella no doubt had a coffered ceiling. Just in front of the doorway, which was fifteen Roman feet wide, are the large stones with holes for the pivots on which the massive double doors swung (indicated in [Fig. 18]); the doors here were not placed in the doorway, but in front of it, and were besides somewhat larger, so that the effect was rendered more imposing when they were shut.
The ornamentation of the cella was especially rich. A row of Ionic columns, about fifteen feet high, stood in front of each of the longer sides; the entablature above them probably served as a base for a similar row of Corinthian columns, the entablature of which in turn supported the ceiling. On the intermediate entablature, between the columns of the upper series, statues and votive offerings were doubtless placed. The floor about the sides was covered with white mosaic, of which scanty remains have been found; the marble pavement of the centre (inside of the dotted line, [Fig. 18]) has wholly disappeared.