The Forum of Constantine was once one of the important locations in Constantinople. Built front of the city gate of Byzantium at the top of the second highest hill of the peninsula, it was part of a series of major construction works by Constantine to expanded Byzantium into the new Roman capital. As the central forum of the city, it also had important structures located on site, including the Column of Constantine (at the center), the Senate House (on the northern side) and a nymphaeum (a monumental fountain on the southern side). Later in the late 9th century a small chapel dedicated to Constantine was built at the base of the column.
Built before the city’s official inauguration in 330, the Forum of Constantine was one of the chief ideological spaces for imperial rule. It was central to the celebrations of the founding of the city on the 11th of May and was located on the triumphal procession, which led from the Golden Gate to the Great Palace. The porphyry Column of Constantine was erected at the center of the circular forum and crowned by a large statue of Constantine, which was knocked off the column by a violent wind in 1106.
Unlike the rectangular forums in Rome, the Forum of Constantine was circular in shape. While unique, circular forums do exist, such as the oval forum in Jerash built around the same time. Dyrrachion (modern Durrës) also had a circular forum built towards the end of the 5th century, which might have alluded to the Forum of Constantine. 
The Column of Constantine is virtually the only remaining trace of the city’s founder, Constantine. A few minor archaeological finds have also survived, which were excavated in 1930. A section of its foundations were found about 70 meters from the column, suggesting that the circular forum had a diameter of 140 meters. Also among the findings were Proconnesian marble paving slabs. However most of what is known about the Forum of Constantine comes from written records. The forum had had two stories of colonnades and two arches of Proconnesian marble leading along the Mese, the main street of Constantinople.
The Senate House in the Forum of Constantine was one of two in Constantinople - the other one was located near the Augustaion.  On the northern side of the forum, it had a porch of porphyry columns. We are told that the Senate had huge bronze doors depicting the gods and giants at war (which might have been brought from the Temple of Artemis in Ephesus). It is possible that it housed a gilded statue of Constantine that was central to the city’s anniversary ceremonies celebrated on the 11th of May. On the opposite side of the forum was the nymphaeum, a monumental fountain decorated with a series of statues. Both the Senate House and the nymphaeum were severely damaged by a fire around 464.
The forum was also decorated by a large number of statues. The statue that captured the most attention and is most reliably attested was a colossal bronze Athena standing outside the Senate House. It has been suggested that this statue was the Athena Promachos or Parthenos from the Athenian Acropolis. Several sources also say that Constantine brought the Palladium  to Constantinople and placed it under the Column of Constantine. The Palladium  was a protective statue that supposedly was first in Troy and later moved to Rome. This was not the only emphasis on Troy; there was also a statue group depicting the Judgment of Paris where the prince of Troy Paris judged which goddess was the most beautiful. There were many other statues, including two bronze female statues on the forum’s western arch which were popularly identified as “the Hungarian” and “the Roman” in the 12th century.