The southern gate of Abritus Late Antiquity castle was placed in the middle of the southern fortress wall. This was the only gate constructed with a recess from the curtain wall – with a view to better defense. The towers to the east and to the west of it were placed asymmetrically: three U-shaped and one rectangular tower to the east of the gate and four U-shaped and one rectangular tower to the west of the gate. That asymmetrical positioning was balanced by a longer curtain wall between southeastern tower 16 and the neighboring U-shaped tower 17 – 45.60 m. The towers stood at roughly the same distance from each other along the remaining stretch of the southern wall. Unlike the other three fortress gates, the towers that flanked the southern gate were not placed right next to it but at a distance of 27.40 m – the eastern one and 26.75 – the western one. The gate was rectangular and had the following size: length 10.76 m (east – west) and width 10.25 m (north – south), it protruded with 5.60 m outside the neighboring curtain walls and jutted into them with 1.05 m. It had two doors: an external descending door and an inner two-leaved wooden door. There was a rectangular room between the two doors – propugnaculum – sized 6 m (east – west) by 5 m (north – south). The openings of both gates was with the same width – 4.30 m. The external door was confined by two pilasters with external length of 0.89 m (the eastern one) and 1.13 m (the western one) and internal length of 0.90 m (the eastern one) and 0.87 m (the western one). Two massive pilasters of the same size stood at both sides of the inside door. From the outside the southern gate and the pilasters were constructed with massive smooth-faced stone blocks connected with iron braces. The inside face was constructed by smaller smooth-faced stone blocks that were tightly pressed to each other. The space between the two faces was filled with roughly cut blocks and white mortar. A water main made of ceramic pipes of different length passed below the floor level of the gate. Just like the northern gate, the southern gate was blocked up with 3 m thick stone masonry in mid-6th century during the reign of Justinian I (527 – 565). A staircase of horizontal lines of stone blocks adjoining the fortress wall led to the platform between the southern gate and tower 20 to the east. The staircase was 12.66 m long and 2.10 m wide. The stairs started at the very northern end of the gate. The staircase was damaged in a serious fire and was later repaired and further built.