Of course, the Roman Empire also left its mark on Istanbul. Some monuments of Roman architecture include the Cemberlitas (Column of Constantine), the Milion, the Valens Aqueduct and the Column of the Goths.
Column of Constantine
Also dubbed the Cemberlitas, this is a major landmark in the city, particularly because it marked the declaration of Constantinople as the 
capital of the entire Roman Empire in 330 A.D. It stands guard at the Forum of Constantine, which is the plaza which is said to mimic the design of the plaza in front of the Saint Peter’s Basilica in Rome. The plaza is lined with colonnades and statues of Christian saints and pagan gods.
The tall column is crowned by a huge statue of Constantine, looking very majestic as Apollo. He stood carrying an orb, which is said to contain a fragment of the True Cross. Later, in 1106, this statue fell due to a hurricane. A cross was erected in the statue’s place, but this was also removed when the Ottoman Empire entered the picture. A fire in 1779 left the column with burn marks, and that is why it was named the Burnt Column.
Now, the column stands at 35 meters. Its scorched yet beloved lines can be seen from as far as the Sea of Marmara. This has been proclaimed as a World Heritage Site on 1985 by the UNESCO.
Valens Aqueduct
The aqueduct, which is also known as the “Aqueduct of the Grey Falcon”, is one of the major suppliers of water during the medieval age. Found in the Fatih quarter, its construction began during the Emperor Hadrian’s reign. It spans 971 meters and 29 meters at its highest. However, 921 meters remain. It is made up of arches, some with single orders, some double. The materials used are ashlar bricks and blocks.
Milion
Another monument featuring Roman architecture is the Milion or the Golden Milestone. This is the monument from which all the other cities’ distances were measured. These distances were then listed as part of the records of the empire. Thus, it was seen as the point from which all roads originated. In addition, the distances of the major cities are written on the monument’s base.
This is found at the Eminonu district of Istanbul, near the old walls of the Byzantium. The Milion is made up of a dome with four arches. It is actually a double triumphal arch. On top are statues of Constantine and Helena, his mother. Justinian added a sundial. Other embellishments include sculptures of Hadrian, trajan and Theodosius.
Sadly, only a portion of this monument remains. A pillar from that monument has been rebuilt.
Column of the Goths
Outside of the Topkapi Palace in Gulhane Park stands the city’s oldest Roman monument . It stands 15 meters high and is made up of marble. It has a base and inscriptions that tell of the Roman victory against the Goths. In addition, it features a Corinthian capital adorned with eagles as coat of arms.