The main gate of the legionary fortress was facing the Danube and the enemy.
The via praetoria led from here to the headquarters, the principia building. The porta praetoria, in its presently-known form, was constructed in the second half of the 3rd century. The gate with three entrances was flanked by two octagonal towers built on circular foundations. Of the three arched entrances the middle one was for vehicular traffic and the two on the sides for pedestrians. The arch of the northern entrance was restored based on carved stones which had survived and its figural keystone was reinstalled. Leading to the Danube, a sewer covered with limestone slabs was built below the road. The bridge across the Danube, connecting the fortress with the bridgehead fort of Transaquincum on the Pest side, could be accessed from the porta praetoria. The remains of the gate can be seen in the archaeological park by 7 Korház Street.