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

The Roman Fort Katzenberg, also known as Römerwarte Mayen, is a late Roman hilltop fortification from the 4th century. Located near Mayen in Rhineland-Palatinate, this complex served as a refuge during the Limes fall, when Germanic tribes advanced into the Roman Empire.
History+
Around 300 AD, the fortification on the Katzenberg was erected after the Roman Limes had lost its protective function. It offered the inhabitants of the then Vicus at modern-day Mayen a safe haven in case of raids. Covering an area of 1.2 hectares, Katzenberg was the largest of about 60 late Roman hilltop fortifications in the Eifel-Hunsrück region. The complex was in use for about 70 years, then paused for 30 years, and used again until approximately 450 AD. A small military post was located on the highest peak, while the lower areas served the civilian population. Discovered around 1900, initial excavations took place between 1907 and 1932.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://de.wikipedia.org/wiki/Datei:Wehrmauer_R%C3%B6mische_H%C3%B6henbefestigung_Katzenberg_Mayen_2010.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: 50.3200, 7.2439