The Roman Castle can be visited
Roman Castle Dörsterberg (Huppert)

The Roman fort of Dörsterberg, also known as the Small Fort Dörsterberg, is an archaeological monument of the Upper Germanic Limes. It is located in the Huppert area of the Rheingau-Taunus district in Hesse, Germany, and is now a UNESCO World Heritage site.
History+
The Roman fortification on the Dörsterberg was discovered in 1897 by Ludwig Pallat. Five years later, in 1902, archaeological excavations began under the direction of the Imperial Limes Commission. These investigations, which ended prematurely due to the death of Felix Hettner, revealed several construction phases. The older complex consisted of a combination of wood and stone construction and was surrounded by a double pointed ditch. The fort's area formed a slightly irregular quadrangle with rounded corners, measuring approximately 23 by 25 meters.
Source: Wikipedia · Licence: CC BY-SA 4.0
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: 50.1975, 7.9950