THE HISTORY
In the mid-eighties of the last century, during the reconstruction of the Library of the City of Belgrade, the remains of the stone foundations of the southeast gate (Porta decumana) of the castrum of the IV Flavian legion were discovered in its basement, and thus this part of the building became known as the Roman Hall. During the stay of this legion, the former Singidunum experienced prosperity and successfully defended itself against the attacks of the Barbarians.
Roman military fortifications (castrum) generally had four gates as the main defence system of the city. For now, two gates of Singidunum have been discovered, one is the southern one, Porta decumana, and the other, the northern one, on the Upper Town of the Belgrade Fortress.
The Porta decumana was a monumental building, 28 meters long, 9 meters wide and it's estimated that it had been over 20 meters high. This made it one of the tallest buildings in ancient Belgrade. It had three passages - a wider one in the middle intended for the quadriga and two smaller ones for pedestrians.
The gate was defended by two rectangular towers. Today, only the foundation of the passage and the northeast tower are visible, while most of the remains are under the Library's premises.
In the interior of the northeast passage, a lead pipe was discovered that served to supply the castrum with water. The water passed through the brick underground channels all the way to the bathrooms, kitchens, fountains inside the castrum.
The ancient remains of two streets in front of the Library were also discovered, which ran from the south-eastern gate through the civilian part of the fortification. These streets partially coincide with today's streets Vasina and Knez Mihailova, which is supposed to have been Via cardo.
Today, this space serves as an archaeological site and a cultural institution, for cultural events.
