The remains of the Castle can be visited
Niedernburg Castle

The castle ruin Niedernburg, also known as Niederburg or Unterburg, is a hilltop castle above the municipality of Kobern-Gondorf in the Mayen-Koblenz district of Rhineland-Palatinate.
History+
The construction of Niedernburg Castle took place around the middle of the 12th century. Its first documented mention dates back to 1195, when the then lord of the castle transferred the property as a fief to the Archbishop of Trier. In the 13th century, the line of the Lords of Isenburg-Kobern died out in the female line of succession. Through the heiress Cecilia, the Kobern castles, along with the lordship, passed to Friedrich II von Neuerburg, a branch of the Counts of Vianden. When this line also died out in the male line in 1309, the castle and lordship were sold to the Archbishop of Trier. The castle met its final fate in 1688 when it was destroyed.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.wehrbauten.de/thread.php?threadid=612
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: 50.3106, 7.4557