The Castello Svevo ('Swabian' or Hohenstaufen Castle) was originally built by the Saracens on the ruins of the ancient Rocca Brutia, around the year 1000. The castle was restored by Frederick II, Holy Roman Emperor, adding the octagonal tower to the original structure, in 1239. According to tradition, his son Henry lived in this castle, as a prisoner at his father's command. Louis III of Naples and Margaret of Savoy married in the castle and they both settled there in 1432.
All signs of the ancient Saracen structure have now disappeared. In the internal cloister, the modifications made by the Bourbons in order to convert it into a prison can also be seen. The entrance-hall is covered by ogival arches with engraved brackets. A wide corridor is dominated by some fleur-de-lis from the House of Anjou coat of arms. They are engraved on the ribbed Hohenstaufen arches.References:
Frösöstenen is the northern-most raised runestone in the world and Jämtland's only runestone. It originally stood at the tip of ferry terminal on the sound between the island of Frösön and Östersund. The stone dates to between 1030 and 1050. It has now been relocated to the lawn in front of the local county seat due to the construction of a new bridge, between 1969 and 1971, on the original site.
Frösö runestone inscription means: Austmaðr, Guðfastr's son, had this stone raised and this bridge built and Christianized Jämtland. Ásbjörn built the bridge. Trjónn and Steinn carved these runes.