The stone headquarters, the principia, stood in the center of the Hunerberg legionary fortress in Nijmegen. Its construction by soldiers of the Tenth Legion (Legio X Gemina) started in the last decade of the first century AD. The legionary fortress lost a great deal of its importance in AD 104, when emperor Trajan decided to move the Tenth Legion to the Danube area. The fortress and its headquarters were abandoned during the second half of the second century AD. It seems likely that the complex was demolished during the successive centuries by either the Romans or the native tribes that took over power.
The principia, measuring 64 x 93 m, was designed to demonstrate the power of Rome and to impress high-rank visitors. The entrance of the complex was architecturally accompanied by an impressive arch of over 15 m in width. The arch framed the view of a statue that stood in the center of a colonnaded courtyard representing most likely emperor Trajan. Based on the analysis of the foundation slabs PANSA BV was able to demonstrate that the courtyard had smaller columns on its sides, whereas larger columns on pedestals were applied on the side opposite the main reception area, which is the basilica.
The architectural finds, like parts of column shafts, Corinthian capitals and the entablature, indicate that the principia was conceived as a representative of formal Roman architecture, like the so-called Harbor Temple in neighboring Xanten (D). Since Roman military architecture in the Netherlands was often considered to have been of primarily utilitarian nature, the high-status Mediterranean articulation of the principia came as a surprise.
The reconstruction of the principia was commissioned by Museum Het Valkhof in Nijmegen. A scale model and various computer stills, all supervised by PANSA BV, are on display in the museum. A computer animated tour guides the visitors of the museum through the headquarters.