The remains of the fortress can be visited
Fortress Koblenz-Werk Glockenberg

The Glockenberg Work, a component of the Prussian Fortress of Koblenz, belonged to the Pfaffendorfer Höhe system. This fortification, originally located in the Asterstein district, is now only preserved in remnants, including a part of the Devil's Staircase.
History+
The Glockenberg Work was constructed in 1822 as a two-story tower in the form of a half-redoubt, south of Fort Asterstein. Around 1900, the facility was abandoned, and the surrounding rampart was leveled after 1906. After World War I, the Treaty of Versailles stipulated the de-fortification of numerous Koblenz installations, including the Glockenberg Work.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://de.wikipedia.org/wiki/Datei:Teufelstreppe_01_Koblenz_2014.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: 50.3505, 7.6106