The fort was built in the current centre of Valkenburg, and was at first fortified by a palisaded earthen wall and three moats. Initially, two maniples (or four "centuriae") of legionaries and two "turmae" of cavalry from the "cohors III Gallorum Equitata" were stationed at the fort. After the Revolt of the Batavi (69-70 AD), however, when the local tribes had razed the fortress to the ground, the entire "cohors IV Thracum" was relocated here. Around 180 AD the Romans enlarged the fort and rebuilt it in stone. In total, 7 building phases have been distinguished.