The remains of the castle can be visited
Hünenburg Castle

The Hünenburg castle remains, also known as Frankenburg, are the ruins of a small, former hilltop castle in the Wesergebirge mountains, near Rinteln in the Schaumburg district, Lower Saxony. It once served to monitor an important pass.
History+
The exact builders and inhabitants of the Hünenburg are unknown, which led to its subsequent naming. Archaeological finds such as pottery shards and horseshoes from 1895 and 1897 suggest a founding between the 10th and 11th centuries. Coins from around 1080, minted under Emperor Henry IV, were discovered on the south side of the palas. The two-part complex, consisting of a main castle and an outer bailey, was designed to secure a pass between the Weser and Große Aue valleys.
Location+
The Hünenburg is situated on a southern spur of the Lange Wand in the Wesergebirge mountains, at approximately 225 m above sea level. It is located in the Weserbergland Schaumburg-Hameln Nature Park, near Rinteln-Todenmann, in the Schaumburg district, Lower Saxony, Germany.
Image: http://www.wehrbauten.de/thread.php?threadid=529
Location: 52.2130, 9.0753