It then followed the course of the Rhine and ended at the Vinxtbach in present-day Niederbreisig, a quarter in the town of Bad Breisig, the border with the province of Germania Superior.

The southernmost and smallest portion, between the Vinxtbach and the area around Bonn still belongs to the Rhenish Massif, through which the river passes in a relatively narrow valley between the heights of the Westerwald and the Eifel Mountains.

From roughly the area of Bonn, the Rhine valley opens into the Cologne Bay, which is bounded by the Bergisches Land, which hugs the river on the right-hand side, and the Eifel and High Fens to the southeast and east.

In the vicinity of the military camp of Novaesium, the Cologne Bay expands further into the Lower Rhine Plain, a river terrace landscape.

[4] The river itself was a crucial means of transport through the region, and became a major supply route to the North Sea and Britain, controlled by the Roman Navy on the Rhine, the Classis Germanica.

[6] This includes forts and marching camps dating back to the earliest arrivals of the Roman army in the area (around 16 BC) as well as development and rebuilding as more permanent fortifications were required at what became a fixed frontier rather than a staging post for the next conquest.

Over the following four centuries the army brought with it industrial and engineering activities (Limekilns, pottery making, roads, canals, a naval base and a water supply aqueduct, for example).

106 individual sites are thus identified, although many of these are grouped as clusters of related features (multiple training camps, sections of canal, etc), giving a list of 44 places.

[9] A number of sites can be matched with Roman place names, particularly from writers such as Tacitus and from ancient documents such as the map known as the Tabula Peutingeriana.