"The forum of Trajan is a perfect miracle, if we inspect it even with the utmost minuteness." Cassiodorus, Variae (VII.6.1)
An immense plaza, measuring almost 380 feet long and 292 feet wide (400 by 300 Roman feet), the forum square was paved in dazzling white marble, partially shaded by four avenues of trees in line with the side porches of the basilica and lateral arches of the boundary wall. The visitor entered the forum through a monumental arch, surmounted with an elaborate chariot group, to confront an equestrian statue of Trajan in the center of the square. Directly behind it was the central porch of the basilica, which duplicated the program of statuary on the arch. And behind them all, the gilded statue of the emperor was visible, crowning the column of Trajan. All in line on the same axis, duplicating and reinforcing one another, the propagandistic effect of such a display would have been unmistakable.
In this plan, the excavated areas of the forum (the east colonnade and hemicycle, the west library and basilica) are highlighted. The hemicycle was paved in polychrome marble set in a pattern of circles and squares, with niches between pilasters along the wall holding statues. The hemicycles must have been roofed to protect the fine marble pavement and statues, which would have been illuminated by windows in the upper story.
The southeastern end of the forum has not been explored and, although a triumphal arch has been presumed to have been in line with the forum's main axis, other reconstructions have been hypothesized, including the placement there of Hadrian's Temple of Divine Trajan. This, it is argued, relates better to the precedent of the Forum of Augustus, where the temple is flanked by its colonnades and their hemicycles, although the location of the arch then becomes a problem.
A major excavation of the forum was initiated by the facist regime of Benito Mussolini from 1928-1934, beginning with what was called the Markets of Trajan. The east colonnade and hemicycle were subsequently cleared, producing a wealth of architectural fragments, which excited public interest and extended the excavation to the western half of the basilica and the west library, many of the gray granite shafts from the lower interior order of the basilica being re-erected then. In 1933, the Via dell'Impero (now the Via dei Fori Imperiali), a processional boulevard, was completed, connecting the Piazza Venezia, where Mussolini addressed the crowd from his balcony, in a straight line with the Colosseum, covering a portion of the imperial fora and effectively dividing them in two.
References: The Forum of Trajan in Rome: A Study of the Monuments in Brief (2001) by James E. Packer.
