Köln-Alteburg: naval base of the Roman Rhine fleet.
Although the city was now no longer a military base, the Roman fleet maintained a naval base, about four kilometers south of Cologne, situated on a hill of about 18 meters high. The site, which is comparatively large (about 7 ha), was founded at the time of Cologne's promotion to the status of colonia and is now called the Alteburg, "the ancient castle". Although the Rhine fleet was created for naval offensives on the North Sea, the ships were almost never used for warfare at all. Instead, they had to control the Rhine, impress the Germanic tribesmen on the other bank, and transported troops and heavy stones.
In c.100, the site was surrounded by a wall of stone. Archaeologists have discovered the barracks of the marines, which were originally made of wood but later constructed from stone as well. The inhabitants - probably some 1,000 men - lived in greater luxury than the legionaries: traces of frescoes have been found in the rooms of the Alteburg.
The shipsheds are almost unique in the northern part of the Roman empire. The only parallels north of the Alps are (to the best of the present author's knowledge) at Haltern on the Lippe and at Velsen in Holland. An interesting detail is the discovery of loom weights and other objects related to the production of textile. This is not very common in a military settlement, but of course the Alteburg must have offered room to velarii ("sail makers").