Košický Castle was probably built in the 14th century although due to many conflicts between the noble family that built it and the king, it didn't get finished. There were also conflicts between its owners and the people of Košice who argued that it was built on their land. In the 15th century it slowly but surely decayed.
It currently serves as a hike destination for people of this region and a place to learn something about the surrounding nature and the history of this place from the information boards.
Wikipedia https://de.wikipedia.org/wiki/Kaschauer_Burg
Address 04001, Slovakia
Coordinates 48°45'43.179" N 21°14'11.398" E