Danube–Iller–Rhine Limes

The Danube–Iller–Rhine Limes (German: Donau-Iller-Rhein-Limes) or DIRL was a large-scale defensive system of the Roman Empire that was built after the project for the Upper Germanic-Rhaetian Limes in the late 3rd century AD. In a narrower sense the term refers only to the fortifications between Lake Constance (Lacus Brigantinus) and the River Danube (Danubius); in a broader sense it also includes the other Late Roman fortifications along the river Rhine (Rhenus) on the High Rhine (between Lake Constance and Basle) and on the Upper Rhine (below Basle til Bingen) as well as the Upper Danube.