The remains of the Castle can be visited
Olbrück Castle

The castle ruin of Olbrück, a landmark of the Brohl Valley, stands on a phonolite cone above Niederdürenbach. It is one of the oldest and largest hilltop castles in the Eifel.
History+
The origins of Olbrück Castle date back to the early 12th century; a mention of a Burkhard von Olbrück in a 1112 document is considered the first reliable reference to the noble family that had its seat here. Ownership of the castle changed frequently, with more than 15 families holding shares in it. In the 14th century, the main tower was built, which today represents the oldest preserved part of the complex. The castle experienced multiple destructions and rebuilds, particularly during the Thirty Years' War in 1632 by Swedish troops and in 1689 during the Palatinate War of Succession by French troops. After the occupation of the Rhineland by French revolutionary troops, the castle was abandoned in 1797 and later used as a quarry.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://de.wikipedia.org/wiki/Datei:Burg_Olbr%C3%BCck_025-.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: 50.4508, 7.1696