Thought to be of Celtic origins, this enormous red-sandstone hilltop castle was first documented in 1081. Between 1125 and 1298 it was the repository of Imperial treasures including, allegedly, a nail from Jesus' cross and tooth from John the Baptist. Richard the Lionheart (Richard I of England) was imprisoned here from 1193 to 1194 for insulting Leopold V, Duke of Austria. Today, the castle's displays include a replica of the Imperial crown jewels. English tours can be arranged.
Recent excavations here have uncovered the remains of a wooden castle believed to date from Saxon times.