Castel del Monte is a true architectural masterpiece and one of the most famous castles in the world (it even features on the Italian 1-cent coin). Constructed by the highly educated, multilingual Emperor Frederick II, there is a definite magical atmosphere to be felt there. To be sure, the inside of the castle is slightly disappointing, since it's completely empty, but the sight of it from far away as you approach it is spectacular. It was not used for a very long time, and then only for falconry, so not much has changed since Frederick's days. The rule of the German dynasty of Hohenstaufen in southern Italy has left many traces there, especially in the form of castles in lots of cities, but none surpass Castel del Monte in sheer beauty and splendor.