The Basilica Nova, also known as the Basilica of Maxentius and Constantine, was a large secular basilica built in the heart of the city along the Via Sacra in the Roman Forum. It was begun by Maxentius and completed by Constantine after 313. The basilica, widely considered a masterpiece, has influenced many architects since the Renaissance. 
As Maxentius was considered a usurper by the Tetrarchs, he began an impressive building program that saw the restoration of temples and other building in the city of Rome in order to gain support from its citizens and help establish his legitimacy. While cities Trier, Milan or Nicomedia were the imperial residences of the Tetrarchy in this period, Maxentius attempted to revive the status of Rome as the imperial capital. The Basilica Nova, arguably the most grandiose of his building project, was begun after he came to power in 306. It was built west of the Temple of Venus and Roma, which Maxentius restored after being damaged by a fire around 306. In addition to building or restoring structures in Rome, he also built a new imperial complex outside Rome on the Appian Way, with its own circus. The Basilica Nova, which was apparently most completed when Constantine defeated Maxentius in 313, was credited to Constantine, as Maxentius was subjected to damnatio memoriae. Constantine, though, oversee its completion, and made a few alterations, including changing the buildings orientation. 
This massive basilica was truly a triumph of engineering. Its design was in many way closer to imperial baths than classical basilicas, as it had huge deeply coffered vaults made of concrete similar to the Baths of Diocletian. The basilica had a plain exterior, with its brick covered in stucco so it look liked ashlar masonry that was typical in late Roman structures. It was around 100 by 65 meters with coffered vaults around 25 meters high. It consisted of a central nave flanked by side aisles divided into three sections that communicating with the revetment and stucco decoration. It was lavishly decorated with marble revetments on its walls, while the floor was paved with colored marble in a geometric pattern of squares and circles similar to that of the Pantheon. Its vaults were deeply coffered in elaborate patterns of octagons, hexagons, and lozenges and decorated with stucco, painted and gilded. The vaults would have appeared like a billowing canopy supported by eight Corinthian columns of Proconnesian marble. Underneath the vaults were enormous windows that lit the interior. In addition, statues were places in the numerous niches in the interior and presumably the exterior as well, though its program is unknown. 
While its original entrance and narthex faced the Temple of Venus and Roma to the east, Constantine made a new entrance with a monumental staircase and four red porphyry columns along the Via Sacra facing the Palatine Hill to the south. Originally the plan of Maxentius had an apse on the west, but Constantine added another apse on the north side of the building which was aligned with this new entrance. The colossal statue of Constantine was placed in the original apse in the west. The fragments of the Colossus of Constantine, now in the Palazzo dei Conservatori of the Capitoline Museums, were found here in 1486. In addition, its sole surviving column was taken to the Piazza Santa Maria Maggiore in 1614. 
Although it continued to be in use later, its original designation was forgotten. Its south aisle and nave probably collapsed in the earthquake around 847. Even though it was in ruins, the basilica had a lasting influence on architecture. It was studied by architects like Bramante, Raphael, Antonio da Sangallo, and Michelangelo, and even had influence on the design of the St. Peter's Basilica.