There are ruins of a strange fortress on an island in a lake called Skeingesjön in the northeast part of Skåne. When you approach the ruins walking in the shadows of mighty oaks, suddenly there are high stonewalls, several meters high. You have to walk along the wall for a while to find the entrance. It is a very small gate, only a metre wide with a sturdy threshold made of stone. When you step inside you can see the holes in the sides of the gateway where once a strong oak beam secured the small gate. There is no other way in or out. The fortress is built in the shape of a perfect octagon with dressed stones in the corners. It is obvious that someone has made a great effort trying to build an impregnable fortress among the lakes and forests in this part of Skåne. But who can this builder have been and why was it built?