The remains of the roman Castle can be visited
Roman Castle Altes Jagdhaus

The Roman fort Altes Jagdhaus was once part of the Upper Germanic Limes. It is in the forests of the High Taunus.
History+
The small fort Altes Jagdhaus was probably built around the middle of the second century AD. It was a stone fort with a slightly trapezoidal layout. The defensive wall, which was 1.7 meters thick on the north side and 2.2 to 2.3 meters thick on the other sides, was constructed from roughly hewn quartzite rubble stones using dry masonry techniques. A ditch does not appear to have been present. The fort had a single gate, oriented north towards the Limes.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Altes_Jagdhaus_1.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: 50.2446, 8.4929