Medieval water fortress.

Near the town of Krupka, two fortresses were built at the beginning of the 14th century as advanced fortifications when the town was founded.
Šejnov fortress was destroyed during the Hussite wars.
Water fortress Starý Dvůr /Althof/ - a fortified residence with a circular floor plan surrounded by a moat. To this day, its remains overgrown with bushes behind the swimming pool in Bohosudov have been preserved.