The porta principalis dextra, in its currently restored form, was built in the second half of the 2nd century.
The rectangular gate towers flank two entrances, each 3.5 metres wide. Smaller repairs and modifications were carried out multiple times on the building. In the last phase of use, in the early 4th century, the eastern entrance was walled up and only the western entrance was used.
The colonnaded road, leading through the gate, was the main north-south road of the legionary fortress, the via principalis, which led to the headquarters, the principia. Tabernae (row of shops) flanked both sides of the road. Behind the tabernae were the barracks of the first cohort of the legion. To the east lay the house of the deputy commander, the senatorial tribunus laticlavius. The reconstructed remains of the southern wall and gate can be viewed in the archaeological park by the south-western exit of the Flórián Square underpass.