Hammershus (castle) built
1200 CE.
Shown on the map at 55.271°, 14.756°.
Hammershus is a medieval era fortification at Hammeren on the northern tip of the Danish island of Bornholm. The fortress was partially demolished around 1750 and is now a ruin. It was partially restored around 1900.
Text from the Wikipedia article Hammershus, licensed CC BY-SA 4.0.