The Basilica Ulpia was composed of a great centralnave with four side aisles, two on each side of the nave. The short sides of the structure formed apses, while the main entrance was via three doorways on the long east front overlooking the Forum of Trajan, which was one meter below the level of the Basilica. The columns and the walls were of precious marbles; the 50 meter high roof was covered by gilded bronze tiles. The east façade featured a portico with three projecting porches. The center porch framed the main entrance and was the grandest, with 10 columns of yellow marble supporting it. Atop the center porch over an elaborate attic and entablature was a gilt bronzequadriga escorted by Victories, with the two flanking porches topped by bigae. Between the chariots were colossal statues of Trajan. The many rows of columns separating the side aisles are a traditional means of structure for basilicas. This method of structure can be traced back to Egyptian hypostyle Halls. The Basilica Ulpia is very similar to one of the most famous hypostyle halls, Great Hypostyle Hall at Karnak. The apse at the northeast end of the Basilica is labelled Libertatis on a fragment of the Marble Plan of Rome, which suggests that it assumed the functions of the Atrium Libertatis, previously located in the Forum Romanum, the place where slaves were legally manumitted. As such there was likely a shrine to Libertas placed in the apse. Many of the columns still exist on site, although a large number have fallen. The whole of the construction was decorated with war spoils and trophies from the Dacian Wars conducted under the command of Trajan. The frieze above the entrance was inscribed with the names of the victorious legions involved in the Dacian campaign. Later, it was used as the architectural prototype by Constantine as the basis for the layout of the new Christian churches. The Basilica Ulpia was used as to model for Constantine completion of the Basilica of Maxentius.
Excavations
The Basilica Ulpia was first excavated by the occupying French government of Napoleon Bonaparte in 1813, after two convents on the site were demolished. In 1814 Pope Pius VII returned from exile and resumed the excavations: it was under Pius that the grey granite columns were reassembled on their bases and walls built to delineate the excavation area. The excavations also uncovered the remains of the pavement made from rare marbles, which gradually disappeared over the course of the 19th century due to rapacious tourists. Clement VII removed several of the yellow giallo antico marble columns which once flanked the doorways of the structure to Saint Peter's Basilica, where they were erected in the transept, while one went to the Lateran Palace. Part of the foundation of the basilica continues today under the modern Via dei Fori Imperiali, a trunk road constructed during the rule of Benito Mussolini.