The reconstruction Kees Peterse created of this headquarters shows a building of surprising size and grandeur. The exquisite computer-generated images bring the atmosphere of the rooms to life and depict details like the imposing entrance gate, the inner courtyard, and the great hall or basilica with the regimental shrine.

Measuring 92.7 by 64.2 meters, the headquarters of the Nijmegen legionary fortress covered an area of nearly 6000m². Many of the remains of this enormous building were uncovered during excavations carried out between 1918 and 1920 and between 1965 and 1967. However, due to the contemporary buildings present on the site, the remains could never be fully investigated.

Analysis of the floor plan showed that many of the measurements in metres could be converted to whole Roman feet based on a Roman foot being equivalent to 29.72cm. For example, the courtyard (17) measures 130 by 156 feet (ratio 5:6) and the wings at the sides of the courtyard and at the front along the main street are 30 and 40 feet wide, respectively. The wing with the great hall or basilica (31) and the rooms behind it is 120 feet wide. In the reconstruction of the upstanding structures, the heights were therefore also calculated as multiples of the Roman foot.

Apart from the basilica (31), four rooms in the floor plan have a special shape. On the longitudinal axis of the building, these are the entrance gate (1 and 2) and the regimental shrine (39 and 40), as well as the two rooms adjacent to the short sides of the basilica (33 and 48). These spaces must also be architecturally accentuated in the upstanding structure. In the reconstruction, the three rooms adjacent to the basilica were given a pitched roof, the ridge line of which is each time perpendicular to the outside wall of the basilica. Seen from the outside, these spaces stand out thanks to the walls being crowned with a triangular pediment with tympanum. A pitched roof has also been reconstructed above the entrance (2) at the front of the building, the gable of which is covered by the superstructure of the grand entrance (1).

The basilica was a wide, rectangular, more or less well-defined type of building in the Roman world. It was a large, elongated hall with a broad and high nave and narrower lower aisles on either side. In the upper part of the nave, the clerestory, daylight entered through windows in the walls. The clerestory could rest on huge full-height columns, sometimes up to 50 Roman feet (almost 15 meters) high. From the floor plan and the foundations of the Nijmegen basilica, it can be deduced that in this basilica a different solution was chosen. Here, there were two rows of ‘stacked’ columns, with the upper columns being generally slightly shorter than the bottom ones.

The regimental shrine (39 and 40) was the main ceremonial space of the headquarters. This is where the legion’s emblems and standard were displayed, as well as the standards of the various cohorts and smaller military units that made up the legion. The adjacent rooms (here 41 and 42) were used to store the pay chests. From the foundation remains it can be deduced that the back of the regimental shrine (40) was raised; presumably, this area was reserved for displaying the emblems and standards of the legion’s military units. Buttresses were erected against the outer walls of the rooms along the back (40-42); these must have served to absorb the lateral forces of a vaulted ceiling covering these spaces.

Buttresses against the walls of the headquarters, at the level of the wing with the basilica, imply that the spaces behind these walls were also vaulted. This form of refinement in the interior is certainly in keeping with the two spaces adjacent to the short sides of the basilica (33 and 48).