Claustra Alpium Iuliarum — Protecting Late Roman Italy

Abstract

Claustra Alpium Iuliarum is a late Roman linear defence system that consisted of walls, towers, and fortresses, and was intended to defend against incursions into Italy from the eastern and northeastern parts of the Empire. In contrast to the outer borders of the Roman Empire, it was constructed in the late third/early fourth centuries inside the borders of the Roman state, along the geographical line dividing northeastern Italy from Illyricum. It lies in the mountainous area of the Julian Alps (uninhabited even in modern times), extending from the northern Adriatic (Rijeka in Croatia) to the Soča valley in Slovenia. The most important via publica between Aquileia and Emona was defended by three linear defence lines. The author presents literary sources and numismatic evidence, as well as the results of archaeological excavations, and points out the chronological problems connected with the construction of this late Roman defence structure.