Roman Town Colonia Ulpia Traiana and Tricensimae

The city was divided into insulae by right-angled intersecting streets. These are modernly numbered from 1 to 40. In the center of the city (Insula 25) was the Forum, which occupied an entire insula.

The insula 26 to the south of it housed the Capitol. It was built in the second century, although the area was previously densely built with houses, some richly decorated with paintings. The actual Capitol extended over a large district. The temple was oriented northeast, towards the Rhine. Only foundations could be excavated, although ruins were still visible until the beginning of the 19th century, and the first excavations in the temple took place during this time.

Northwest of the Forum were the thermal baths, which in turn occupied an entire insula (10). The so-called administration palace, whose function has not yet been sufficiently clarified, occupies the three insulae (4, 11, and 17) west of the Forum. Other important public buildings were the amphitheater in the south of the city (Insula 40) and a large temple at the harbor (Insula 37). A smaller Matron sanctuary could be excavated within the residential area (Insula 20).

The individual insulae of the private residential and commercial areas were parceled out. The individual plots were approximately 12 x 44 m in size. These are mostly strip houses. The houses were partly richly decorated with wall paintings, but there is no evidence of mosaics so far. No atrium or peristyle houses have been found so far either. In these respects, the city differs significantly from Cologne. In Insula 3, a larger residential house was excavated, which with its corner projections resembles a Villa Rustica rather than a townhouse. The building was over 20 m long, with the corner projections oriented towards the courtyard, while there were colonnades on the street front. Some rooms of the house had hypocausts. In Insula 19, several residential buildings were excavated. Here, some high-quality wall paintings were found, including the so-called Eagle-Giant wall.

The numerous wells found in the CUT area alone were naturally not sufficient to supply a city of this size with adequate amounts of drinking and utility water. Although remains of water pipes were found in some places in the Xanten area as early as the 19th century and then after the Second World War in the Xanten urban area itself, they did not show a clear connection for a long time. However, only the "Hees" or the "Sonsbecker Höhen" could be considered as water catchment areas.

In 1959, Hermann Hinz discovered a pipeline that reached the CUT from the south, leading from the terminal moraines of the "Hees" through present-day Xanten and along the former grave road. Finally, in 1975, in connection with road construction measures in the Labbeck district of Sonsbeck, a section of the supply line was found, which served to transport surface water from the Sonsbecker Höhen to the CUT. It was a mortar channel mixed with brick fragments, which still contained traces of the typical lime sinter. The foundation was solidly built from Eifel greywacke, basalt, and tuff stones. Slate plate fragments indicated the former covering of the channel, which had a gradient of 20 cm per 100 m. Part of this water pipeline was relocated and preserved in the Archaeological Park Xanten.

In May 2007, during dry weather, aerial surveys by aerial archaeologist Baoquan Song (Ruhr University Bochum) showed clear vegetation anomalies, indicating an aqueduct pillar row in the so-called "Furth". Further indications of sections of the water pipeline were found at the Hasenacker forester's lodge. Excavations in December 2008 confirmed the aerial images. During construction work in the area of Xanten market square at the end of 2009, remains of the water pipeline foundations were found.

Tricensimae was the name of a large Roman fortress of late antiquity in Xanten on the Lower Rhine. Its name could indicate the continued existence of Legio XXX Ulpia Victrix until this time.

The camp was built between 306 and 311, probably under Emperor Constantine, on the 9 central insulae of Colonia Ulpia Traiana. It was 400 by 400 m in size, had 4 m thick walls with 48 towers, and was surrounded by two ditches. However, the building material was not brought from afar, as was the case with the construction of the Colonia. Stones were finally available directly outside the gates. Furthermore, clearing the forefield also had a military purpose. Every ruin was a visual obstruction for the defenders and also a potential hiding place for attackers. The reason for the strong fortification was probably the danger posed by plundering Germanic tribes.

In 352 AD, Tricensimae was conquered by the Franks and rebuilt from 359 AD. In the first half of the 5th century AD, the settlement was finally abandoned. It was probably too insecure despite the thick walls.