The Devil's Castle, surprisingly tame now
Despite the name, the Geeraard de Duivelsteen — Gerard the Devil's Stone — was built in the 13th century as a nobleman's home, not a hellmouth. Over the centuries it's been a prison, an armoury, a monastery and a school, which is a lot of careers for one grey building. The nickname probably stuck because Gerard was, by all accounts, not a soft touch. Look up at the towers and picture the many moods this place has had.