The earth and timber rampart of the Oberaden legionary fortress
Based on Kees Peterse’s 3D reconstruction, the walls of this enormous Roman fortress were physically reconstructed in 2012 over a length of almost 60 metres, full scale and in situ. Soil stains (remaining traces in or on the ground) and other excavated remains made it possible to make a very detailed reconstruction, right down to the timber construction and the joints used.
Map of the Roman fortress at Oberaden. Drawing, LWL-Archäologie für Westfalen/D. Jaszczurok; graphic rendering by PANSA BV.
The remains of an enormous Roman fortress, large enough for two to three legions are located in Oberaden, in the municipality of Bergkamen in Germany. This fortress was built deep in enemy territory towards the start of the Augustan Roman Wars, in 11 BC. Three or four years later it was dismantled and abandoned. The fortress covered approximately 56 hectares and was surrounded by a fosse (ditch) and rampart with a total circumference of approximately 2.7 kilometres. Even after more than 2000 years, the ditch and the earth infill of the rampart are still visible in some places as a shallow trench and slightly elevated ground.
Course of the ditch and rampart on the north side of the Oberaden fortress, and map of the sections excavated in 2003 to 2010, including the gate (1) and two towers (2). Drawings, LWL-Archäologie für Westfalen/D. Jaszczurok & B. Tremmel; graphic rendering by PANSA BV.
Left: reconstructed cross-section of the ditch and rampart. Drawing by Kees Peterse.
Right: view over the course of the ditch and rampart, still recognisable as a shallow trench and slightly elevated ground. Photo by Kees Peterse.
In 2005, Kees Peterse was commissioned by the Verein der Freunde und Förderer des Stadtmuseums Bergkamen (Friends and Supporters of the Bergkamen Museum) to make a 3D reconstruction of the rampart and towers, with the aim of using this to reconstruct, in situ, a full-scale section of the wall and one of the towers. This project was completed in 2012.
The supports for the timber structure of the rampart were formed by 15x20cm posts set in two parallel trenches dug 3 metres (10 Roman feet) apart. Along the course of the rampart, the posts were set at intervals of 1.2 metres (4 Roman feet). Each set of opposing posts across the width, connected with tie beams, formed a truss. Planks, in the reconstruction measuring 3x20cm and 2.4m in length, were attached to the posts on the inward-facing side of the ‘corridor’.
Design for the reconstruction of part of the rampart and reconstruction of a cross-section of the rampart. Drawings by Kees Peterse.
The space between the two wooden walls was filled with material excavated when digging the ditch around the rampart. From the shape and dimensions of the ditch it can be calculated that the earth filled the space between the two wooden walls to a height of approximately 2.6 metres. Partly based on references from ancient writers and remains found elsewhere, in the reconstruction of the Oberaden wall a height of 3 metres (10 Roman feet) was used; that’s to say, that’s the height at which the uppermost tie beams of the trusses, those which would support the parapet walk, were secured.
In his 3D reconstruction, in the space between the top of the earthen rampart body and the wooden floor of the parapet walk Kees Peterse included an element for the drainage of rainwater in the form of wooden gutters leading to scuppers in the exterior part of the rampart, directing the water to the ditch. This feature was not included in the physical reconstruction of the rampart. Based in part on remains of timber structures found in Oberaden, Kees Peterse reconstructed the tie beams in the trusses as anchor beams, attached to the posts using mortise and tenon joinery, with the tenons extending through the posts. In the physical reconstruction of the rampart, only the top tie beams are designed as anchor beams.
Left: reconstructed exterior view of the rampart. Still rendering by Gerard Jonker.
Right: reconstructed section of the rampart with tower, with photo taken shortly after completion in 2012. Photo by Kees Peterse.
Reconstructed interior view of the rampart. Still rendering by Gerard Jonker.
The panelling on the rampart is fitted on the inside of the posts as to better withstand the outward pressure of the earthen core. In the reconstruction, the parapet on the outside of the parapet walk has been secured to the outside of the posts. As a result, the transition between the wall of the rampart and the parapet walk was also visible on the outside, similar to how in masonry walls this transition was usually marked by a cordon. Securing this part of the parapet to the outside of the posts also made it more resistant to the impact of projectiles.
In the reconstruction, the parapet has been given man-sized merlons (the solid sections) rising 1.8 metres (6 Roman feet) above the floor of the parapet walk. The crenels (spaces between the merlons) rise to a height of about 1 metre. The merlons fill the space between two posts, meaning these are 1.4m wide. The rhythm of the posts in the rampart also determines the width of the crenels. In the reconstruction, the crenels are 2.2m wide. Elsewhere, too, the sum of the widths of merlons and crenels is often 10 or 12 Roman feet (3 or 3.6 m).
In principle, the parapet, as well as the rampart itself, may have been panelled with planks; however, numerous remains of loam-covered latticework have been found in the ditch, and this may also have been used for the parapet. This ‘wattle and daub’ covering would also offer protection against fire, for which the open parapet walk was much more vulnerable than the earth-filled rampart. During the reconstruction of the rampart in Oberaden, wattle and daub was used for the parapet.
Left: reconstruction of the parapet walk showing the parapet and towers. Still rendering by Gerard Jonker.
Right: towers on the rampart at a Roman fortress depicted on Trajan’s Column (scene 51) in Rome. Photo: www.trajans-column.org.
Wooden towers were erected along the rampart every 80 Roman feet (approx. 23.5 metres). These were as wide as the rampart but protruded slightly inside the fortress. In the reconstruction, the shape of the towers has been derived from the reliefs on Trajan’s Column in Rome, a triumphal column depicting campaigns against the Dacians in the Balkans. The towers were built using four posts to support a platform measuring 10 by 12 Roman feet (3 by 3.6 metres). In the reconstruction, the platform of the towers rises 3 metres (10 Roman feet) above the parapet walk. The towers were not covered and were enclosed by open railing rather than a parapet.
The rampart with tower, reconstructed in 2012, is now part of Römerpark Bergkamen (located at Am Römerberg 1, Bergkamen-Oberaden).
To learn more
K. Peterse, Die Rekonstruktion der Holz-Erde-Mauer des Römerlagers Oberaden, BABesch 85, 2010, 141-177. [PDF]
K. Peterse (†) & B. Tremmel, Holz und Erde. Die Holz-Erde-Umwehrungen der römischen Militärlager Bergkamen-Oberaden und Haltern-Hauptlager, in: E. Claßen, M.M. Rind, Th. Schürmann & M. Trier (Hrsg.), Roms fliessende Grenzen. Archäologische Landesaustellung Nordrhein-Westfalen, Darmstadt 2021, 465-473.