The remains of the Castle can be visited
Unterburg Castle (Ruin) (Driedorf)

In Driedorf in the Lahn-Dill district, the Unterburg ruin, also known as Junkernschloss, is located. It was once a moated castle.
History+
Before 1280, a property of the Lords of Greifenstein was located at this site in the Rehbach valley. Following a dispute, the possession fell to Otto I of Nassau, who had a square moated castle with a courtyard and palace built on the remains between 1280 and 1290. From 1303, the castle served as a residence for Count Emich I of Nassau-Hadamar. He obtained town rights for the adjacent settlement in 1305. In 1347, the castle was acquired by Otto II of Nassau-Dillenburg, who enfeoffed it to the noblemen Johann and Wiegand von Mudersbach, after which it received the name Junkernschloss.
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: 50.6323, 8.1854