Colonia Ulpia Traiana, Roman settlement remains in Xanten, Germany

Colonia Ulpia Traiana is a Roman city site in Xanten laid out on a rectangular grid of insulae, with a forum, a Temple of Jupiter, baths, an amphitheatre and a harbour temple. Its 73-hectare area is now the Archaeological Park Xanten, where reconstructed sections stand beside excavated foundations and a long grey wall with engaged columns and cylindrical column stumps.

The site began as a Cugerni settlement near the legionary camp Vetera, founded in 13/12 BCE by Drusus; it burned in the Batavian revolt of 69/70 and was rebuilt from 71. Around 100 Trajan raised it to a colonia, prompting a near-total rebuild with a grid plan, forum, temples, amphitheatre and water supply. It was sacked by the Franks in 276, and Constantine built the fortress Tricensimae on the site between 306 and 311.

The name Colonia Ulpia Traiana honours Emperor Trajan, who granted city rights around 100 CE. Residents held Roman citizenship, and veterans of the legion at Vetera received land and formed a wealthy class. Excavations found pottery kilns near the harbour and silver-working workshops in Insula 39.

The park lies on the site of the ancient city in Xanten, with the LVR Roman Museum at its centre; reconstructed buildings stand on the original street grid, so the chessboard layout of insulae, cardo and decumanus can be followed on foot. Excavation continues in parts of the 73-hectare area, and the burial ground inside the walls shows graves once lay outside the settlement.

The site is part of the Lower Germanic Limes UNESCO World Heritage designation, recognized for its role as a historical border of the Roman Empire along the Rhine River and its importance in demonstrating Roman frontier engineering and defense strategies in northern Europe.