The headquarters of this Classis were established in 12 BC by Drusus[2] and controlled the Rhine river: it was mainly a fluvial fleet, although it also operated in the North Sea.

After 30 AD, the fleet moved its main base to the castrum of Alteburg, some 4 km south of Colonia Claudia Ara Agrippinensium (modern Cologne).

Colonia Ulpia Traiana was defended by huge walls 3.4 km long and with 22 towers[4] During the whole 2nd and the first half of the 3rd century this Roman colony was involved into a continuing process of urbanization and architectural improvement.

Recent archaeological excavations in the area of the Capitolium-temple, Harbor-temple, Roman Baths and Forum brought numerous fragments of veneering slabs of marble to light, which once lavishly decorated walls and floors of these public buildings.

Meanwhile, in 363 AD, during the reign of Julian, the Christian Viktor of Xanten is supposed to have been executed together with 360 other members of the Theban Legion near the modern town of Birten for refusing to sacrifice to the Roman gods.

In the second half of the 8th century a church was built on the grounds of an old cemetery of the ancient Roman colony and called Sanctos (super Rhenum) (also mentioned as "Ad Sanctum").