Hammershus

Hammershus is Scandinavia's largest medieval fortification, situated 74 metres (243 ft) above sea level on Hammeren, the northern tip of the Danish island of Bornholm in the Baltic Sea. Erected in the 13th century, it was long believed that the castle was built as a private residence for the archbishop of Lund. However, new evidence found at the ruins of the castle suggests it was constructed in the beginning of the century as a royal residence for Valdemar II of Denmark and a base for the Danish crusades, according to Kjeld Borch Westh, superintendent of the National Museum of Denmark.

• http://en.wikipedia.org/wiki/Hammershus