The original Allmendingen Castle was built during the High Middle Ages probably for the Lords of Allmendingen or Alwandingen. Between 1239 and 1256 Rudolf von Alwandingen was mentioned in the record. In 1256 the Lords of Allmendingen sold both Allmendingen and the neighboring hamlet of Märchligen to Interlaken Abbey. The castle fell into disrepair and during the 16th century the cartographer Thomas Schöpf referred to it as a arx disruta or broken castle. In 1676 Albrecht Kauws mentioned the ruins of Alt-Allmendingen Castle and by 1729 the ruins were still visible. The old castle had walls that were about 2.1 meters and was a square with 9 meters long walls. The south and west side had no windows.
After the Protestant Reformation in 1528, Interlaken Abbey was secularized and its lands, including Allmendingen, were taken by Bern. A new Allmendingen Castle was built near the old castle during the 16th or 17th century. One clue as to the construction date is that a door in the tower bears the year 1607. The new castle was built for the Graffenried family in the Renaissance style. The tower was initially topped with a high pointed roof, which was later replaced with a lower one. In the 18th century, the castle was renovated by the Schultheiss Isaak Steiger and then by his son Franz Ludwig. They expanded the castle with a garden court yard and a connecting arbor.
On 17 September 1946 Winston Churchill visited Allmendingen Castle.
References:Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.