The huge residential tower of very unusual construction is the centre of the fortifi cation of the royal castle. Its three meters thick walls of black square stones were even more reinforced by spiked blades on which the projectiles catapulted by trebuchets and fi re arms under a sharp angle slid down without doing serious harm. The castle had been seized neither in the early Middle Ages nor during the Thirty Years’ War. The lovers of mysteries allege that it is due to the mysterious protective symbols carved in the low 11 rows of the tower stones. Although they really look like runic letters, the historians only see the marks of the stone cutters who worked on royal constructions in them. But who knows?