The Upper Germanic-Rhaetian Limes of the Roman Empire

The Limes Germanicus (Latin for Germanic frontier) was a line of frontier (limes) fortifications that bounded the ancient Roman provinces of Germania Inferior, Germania Superior and Raetia, dividing the Roman Empire and the unsubdued Germanic tribes from the years 83 to about 260 AD. At its height, the limes stretched from the North Sea outlet of the Rhine to near Regensburg (Castra Regina) on the Danube. Those two major rivers afforded natural protection from mass incursions into imperial territory, with the exception of a gap stretching roughly from Mogontiacum (Mainz) on the Rhine to Castra Regina.

The Limes Germanicus was divided into:

The total length was 568 km (353 mi). It included at least 60 forts and 900 watchtowers. The potentially weakest, hence most heavily guarded, part of the Limes was the aforementioned gap between the westward bend of the Rhine at modern-day Mainz and the main flow of the Danube at Regensburg. This 300-km wide land corridor between the two great rivers permitted movement of large groups of people without the need for water transport, hence the heavy concentration of forts and towers there, arranged in depth and in multiple layers along waterways, fords, roads, and hilltops.

Roman border defences have become much better known through systematic excavations financed by Germany and through other research connected to them. In 2005, the remnants of the Upper Germanic & Rhaetian Limes were inscribed on the List of UNESCO World Heritage Sites as Frontiers of the Roman Empire, with lower Limes being placed on the tentative list in 2011, aiming to extend the world heritage site to the whole limes. The Saalburg is a reconstructed fortification and museum of the Limes near Frankfurt.

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