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 smal