The present contribution considers the Pannonian ‘inner fortifications’ in the context of the development of the infrastructure and urban fabric of selected sites on the Lower Danube. Using Sándor Sopronis’ thesis, which postulates that a multiple defensive system gradually expanded in Pannonia after the time of the Tetrarchy, as a starting point, this study concentrates on the inner fortifications founded in the middle third of the 4th century AD in the hinterland of the Limes (Környe, Tác / Gorsium, Keszthely-Fenékpuszta and Alsóheténypuszta) which, together with towns such as Sopianae, Mursa, Cibalae, Sirmium und Bassianae, constituted an inner line of defence. Whether they functioned in a civil or purely military context is a subject that has been, and still is, much debated. However, they appear to have played a significant role in the storage, distribution, and perhaps production, of the annona. A similar situation can be observed on the Lower Danube, in the provinces of Dacia Ripensis, Moesia Prima and Scythia. Here too a series of castra and towns, which took on similar functions in the course of the 4th century AD, are found some 30 to 50 km from the frontier. This area however saw a further development well into the late 6th century AD: several sites continued to play a central role as the sees of bishoprics in the Early Byzantine Period. The examples of Abritus and Tropaeum Traiani, which both possess elements that are strikingly similar to the Pannonian establishments, are used here to gain insights into the processes at work and to discuss the structural parallels comparatively.