Frederick II (who also built Trani Castle, among others) built a mysterious hilltop monument that can best be called a castle - but probably was never intended as a defensive structure or even a palatial residence. In fact, not much is known about the reason for its existence, other than its grand statement of beauty and power.
The castle was built during the 1230's in the form of an octagonal prism, with octagonal towers on each of the eight points. The design is somewhat unusual, and is thought to be a metaphorical translation of the relationship between square earth and circular sky. The structure was originally faced with marble (instead of the current sandstone), but it was stripped by vandals along with much of the interior. We weren't allowed to photograph the rooms inside, so we didn't linger and aren't able to show you what they look like.
The building is barely defensible, having no moat and only a small, poorly protected door as an entrance. It wasn't necessarily built as a palace, though, because there is no kitchen and few creature comforts inside. It is thought that king Frederick built it partly as a hunting lodge and partly as a religious and monarchial symbol. Not much is known about his purpose, though, or about the people who designed and built it for him.
It's location is impressive enough - the walls are visible for several miles in all directions, on top of the hill. The land rises up out of olive orchards and some rocky, sparsely-grassed pastures. We drove along roads bounded on each side by ancient stone walls and wound our way towards our goal on a bright, hot afternoon in March. It wasn't too disappointing that we weren't able to get better pictures because the experience was so strangely beautiful.