Study of the walls parameters and analysis of the buildings

The geometric shape of the town enclosure is a simple polygon. The often uneven feature line is obviously adjusted to the ground - a favourable development site and an economic opportunity for construction of the town moat. It was probably intended to keep an adequate part of the overall area to the west of the Langgasse. The area could be likened to any polygon with a side length of about 116 fathoms (approx. 212m), about 201 fathoms (approx. 368m) on the east, about 243 fathoms (approx. 444m) on the south and about 264 fathoms (approx. 484m) on the west sides.
The area enclosed by the town borders is almost exactly 40,000 square fathoms (approx. 13.4 ha). It can therefore be roughly calculated that there is the same space between the theoretical fundamental rights of the town (approx. 339m x 403m) and the course of the town’s actual borders.
Changing this into an equal-sided square gives a side length of about 200 fathoms (approx. 366m). The task might therefore have been to build a town with an area of 200 x 200 fathoms. The deviation between execution and the basic rectangle was due to the surface conditions.
The position of the defence towers in relation to each other can also be explained by the basic rectangle. That is how, for instance, the spire, the Obal-tower and the marking point A of the town (starting point for the measurements) make a right-angled triangle. The flight of the spire also leads through the marking point A of the town and through the south-east corner tower (tower at the devil’s hole – or Kapuziner Bastion). This straight line can therefore be seen as the marking line to determine the south-east corner tower on the ground. The former function of the spire as a defence tower is proven by the geometric relationship between the single points.
Together with the town wall, the defence tower is an essential part of the medieval town fortress. The wall leans slightly inwards, i.e. its thickness decreases as its height increases. At various heights, the wall thickness measures between 1.47m and 1.31m.
During the Renaissance, a completely new order of old defence building became necessary because of the invention of artillery. All of a sudden the high town walls no longer provided sufficient protection - a wide glacis had to be kept free to be able to recognise attackers from afar and to fend them off. The cannons needed larger spaces to manoeuvre in and the reaching area of the shots (max. 200m) determined the required distance (max. 400m) and number of bastions. The cannons were positioned on these bastions, where the ammunition was also kept, either inside or to the side. Domenico dell’Allio was entrusted with management of the site. The main characteristics of this Renaissance fortress were its bastions, curtain walls and a deep moat.
Between the bastions and curtain walls, ravelins were installed to provide another possibility (apart from the bastions) to bring besieging batteries under crossfire.
Bastions were placed on the prominent corners of the fortified polygon and were connected to each other by the curtain walls. This earthwork and masonry construction measured a height of between 10 and 14 metres from the lowest point of the town moat. The moat was particularly important in this system. It was extended, deepened and filled with water from the Prentl-Muehlgang. For this reason, it was necessary to deviate the branch of the Mur which flowed from the main river bed into the town moat, and to install weirs so as not to wash out the Clergymen’s Bastion during flooding. The excavation material was thrown out in front of the old ring wall and then up against the Renaissance wall.
Because the rampart and the moat were 5-7 m below its base, the curtain wall reached a height of approximately 10m.
A particular disadvantage was that the district of the town – the suburb of Gries - was not connected (contrary to what Martin Stier had recommended) to the fortified Oberradkersburg Castle lying opposite it, and so it was necessary to defend two separate areas. This weakness in the whole system was never really improved, but luckily it never had to play a role in affairs.
There are still some very well-preserved parts of the wall, such as the area of the Hollow Bastion, the Secondary School, and the western edge of the town (between the Obal tower and the spire).
It is presumed that there are remains of the town wall foundation lying below the surface even today.