English: The ruins of the Triumphal Arch of Theodosius.

The marble pieces that are located here belong to the Triumphal Arch and the forum built by and named after Emperor Theodosius the Great (4th century CE). The Triumphal Arch was situated on the southwest corner of the Theodosius Forum (today Beyazit Square). This area used to be called "Forum Tauri" (The Bull Square) but in the 4th century CE the name was changed into the "Forum of Theodosius". During this period, the forum was surrounded by marble public and civil buildings decorated with porticoes.

The marble archeological pieces that can be seen today were found between the years 1948 and 1961 during the rearrangements of Beyazit Square and Ordu street. After the discovery of these pieces, an experimental reconstruction was made in spite of the absence of some pieces and finally the probably form of the monument was established. According to this reconstruction, the triumphal arch had a vaulted roof with three passageways. The central one was higher and the ones on either sides lower. It was conceived to be similar to the ones in Rome. In the middle was the statue of Theodosius, while on both sides statues of his sons were put up, Arcadius and Honorarius.

Today the main street that starts from the Hagia Sophia Square is basically in the same direction to the west with the ancient Mese road, which formed the main artery of the old city. The Mese, passing through the Theodosius triumphal arch continued on to Thrace and reached out the Balkan peninsula. The triumphal arch and the surrounding ancient buildings to which some ruins possibly belong were destoryed as a result of invasions and natural disasters like earthquakes from the 5th century on. Thus their destruction was completed long before the conquest of Constantinople by the Ottoman Turks.