The Basilica Ulpia became the most important civic-basilica when it was constructed. It replaced the central role played by the two late Republican period basilicas built in the Roman Forum, the Basilica Julia and Basilica Aemilia. Basilica Ulpia remained the central hub of the civic activity until the Basilica of Maxentius was constructed in the Forum Romanum in the early 4th century CE (circa 310-312 CE).

At the time of its construction it was the largest civic-basilica in ancient Rome, measuring approx. 117 by 55 meters (385 x 182 feet). It served as a primary venus for the administration of justice, commerce and the presence of the emperor.

Later, it was used as the architectural prototype for 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.

circa 112 CE - Modern Period

Roman Empire Period (112 CE-Late Antiquity)
The Basilica Ulpia was constructed under Emperor Trajan and inaugurated in 112 CE as part of his Foro di Traiano. It served as a judicial and administrative center, housing tribunals and commercial activities. Architect Apollodorus of Damascus designed it with a vast rectangular plan, a double colonnade, and exedrae at the ends. The basilica remained a vital hub of Roman civic life until the decline of the Western Roman Empire (5th century CE). With the sack of Rome in 410 CE by the Visigoths, its condition deteriorated, though it was still partially in use in the early Byzantine period.

Medieval Period (5th-15th Century)
As Rome fell into decline, the Basilica Ulpia suffered from neglect, repurposing, and systematic spoliation. By the early Middle Ages, large portions of its marble and columns were stripped for use in churches and palaces. The area was gradually covered with debris, and by the 8th century, the ruins were largely buried under newer constructions. Unlike some other ancient basilicas, it was not converted into a church, hastening its decay.

Renaissance Period (15th-17th Century)
The Renaissance revival of classical antiquity led to renewed interest in Roman ruins, including the Basilica Ulpia. Humanist scholars and architects like Leon Battista Alberti and Andrea Palladio studied its remnants, influencing Renaissance architectural principles. However, the basilica was also a victim of large-scale quarrying, during the Renaissance period. 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. Later on Pope Paul III (reigned 1534–1549 CE) and other Renaissance popes used its marble and columns for Saint Peter's Basilica and other Vatican building projects.

Modern Period (18th Century-Present)
Serious archaeological excavations began in the 19th century, uncovering portions of the basilica’s flooring, columns, and foundations. Systematic studies and restorations continued into the 20th century, particularly under Mussolini’s Fascist regime, which sought to highlight Rome’s imperial past. Today, the basilica remains partially excavated, with its towering columns standing as a testament to its former grandeur. It remains a key part of Rome’s archaeological landscape, offering insights into Roman civic architecture and the evolution of basilicas.

circa 112 CE

The core of the Basilica Ulpia's floor plan was of typical Roman style which composed of a great central nave with side aisles, two on each side (four in total) of the nave. The short sides of the elongates structure ended in apses, while the main entrance was via three doorways on the long east front overlooking the Forum of Trajan, which was appox. one meter below the floor level of the Basilica. The columns and the walls were of precious marbles; the 50 meter (164 feet) 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 bronze quadriga (four-horse chariot) escorted by Victories, with the two flanking porches topped by bigae (two-horse chariots). Between the chariots were colossal statues of emperor 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 as Libertatis on a fragment of the Forma Urbis Romae, a Severan period marble plan of ancient 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.

Several of the original columns still exist on site. 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.

circa 1800 CE- Modern Period

The Basilica Ulpia was first excavated by the occupying French government of Napoleon Bonaparte in 1813, after two convents on the site were demolished (Santo Spirito and di Santa Eufemia). 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.

Most of the structural details of the basilica building along with the Trajan's Forum came to light during the major campaign of excavation financed by Italy's fascist government and conducted by Corrado Ricci conducted during 1928–34 CE. These excavations largely defined the plan of the forum and its buildings, with the exception of the area of the Temple of Trajan.

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.

The reconstruction of the basilica, planned by former Rome Mayor Ignazio Marino in 2014, began in 2021. The work will be carried out by the method of anastilosis, in which the ruins are restored using the original architectural elements. The funds for the reconstruction in the amount of 1.5 million euros were donated by the Uzbek-Russian oligarch Alisher Usmanov.