The Roman site of Carnuntum was once a flourishing center on the frontiers of the Roman Empire. In its heyday as the capital of the province of Pannonia superior, Carnuntum probably covered an area of almost 9 km². The whole site was divided into a military settlement (castra and canabae legionis) and a civil town (municipium/colonia). Through a large-scale archaeological prospection project, this huge area could be investigated and analyzed in great detail using a wide variety of nondestructive prospection methods. One of the main discoveries of the project was observed in the military settlement, where it was possible to identify a previously unknown military camp, interpreted as the garrison of the governor’s guard, the castra singularium. Through the topographic analysis of the immediate surroundings, the Roman fort was determined to be embedded in a large administrative complex related to the governor’s seat in Carnuntum. This article presents these new discoveries and shows what an important part they formed in the administration of the Roman province of Upper Pannonia.