A first wall ring was built around 1200. However, this first wall ring was difficult to defend because of its vastness and the city of Friesach was conquered three times in 1275, 1289 and 1292. The decision to build the new, smaller curtain wall was made in the 13th century. The Sankt Veiter and the Neumarkter Tor were demolished in the course of the road widening in 1845, the Olsator in 1873 after the construction of the train station in 1873.
The second circular wall with a trapezoidal floor plan is around 820 meters long and extends at both ends to the Berglehen on Virgilienberg and Petersberg and includes the fortifications on Virgilienberg and Petersberg.
The city fortifications consist of the actual wall, ten to eleven meters high, and a lower wall in front of it about nine meters away. This is followed by a city moat about 15 meters wide and almost ten meters deep, which is dug into the slope on Petersberg. The moat is fed from various groundwater sources and used to flow into the city sewer system, today the drain is at the southern end of the moat. The lower parts of the wall date from the late 13th century, younger sections from the first quarter of the 14th century, most of the Zwingermauer and the battlements from the 15th century. In addition to the northern Neumarkter Tor, the eastern Olsator and the southern Sankt Veiter Tor, the fortifications on the slope west of the Virgilienberg had the Heidentor and between Rotturm and Petersberg the Sacktor, which still exists today.