Neuenburg Castle originally had three mediaeval round towers. The only one remaining today is the mighty keep known as “Dicker Wilhelm” (Fat William).
Work began on the tower in 1150. With walls that are 2.85 metres thick, it measures 14 metres in diameter and is 23 metres high at the base of the roof. The historical entrance leads directly up to the vaulted main floor. The ground-level entrance was only added in the 16th century. The advanced amenities, with a fireplace and latrine, suggest that “Dicker Wilhelm” was used both for defensive purposes and as a living-place. The original slated domed roof dates from 1550. The keep was restored in 1983; since 1991 it has been part of the tour of Neuenburg Castle, holding special exhibitions and acting as an observation tower.