The remains of the roman Castle can be visited
Roman Castle Bodobrica

In Boppard, Rhineland-Palatinate, the Roman fort Bodobrica stands as a testament to late antique Roman military architecture.
History+
Roman presence in Boppard dates back to the 1st century, with the settlement mentioned in historical sources from the 2nd and 3rd centuries as Bouobriga or Bontobrice, likely based on an earlier Celtic settlement. Around the mid-4th century AD, the Bodobrica fort was built to protect the Roman Rhine border from Germanic tribes. This fortress, approximately 308 by 154 meters in size, served as a military base and trading post. Unlike other forts along the Middle Rhine, Bodobrica was constructed as a planned structure on open ground. Its walls, some up to nine meters high and three meters thick, were reinforced with presumably 28 round towers.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://de.wikipedia.org/wiki/Kastell_Boppard#mediaviewer/Datei:R%C3%B6merkastell_Boppard.jpg
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 50.2310, 7.5916