Altensteig Castle probably dates back to the 12th century. In 1287, the castle was first mentioned as being owned by the Counts of Hohenberg. Hermann, son of Margrave Rudolf of Baden, conquered the town but had to return it to Count Burkhard von Hohenberg in 1288. In 1398, the Hohenbergers sold the Lordship of Altensteig to the Margraves of Baden. The castle became the seat of the Baden bailiffs.
In 1603, as part of a territorial exchange, Altensteig came under the rule of the Duchy of Württemberg. From 1605, Heinrich Schickhardt built the New Castle as the administrative and residential seat of the Württemberg bailiffs. The old castle served as a grain silo from the 18th century onwards. The lower part of the striking residential tower, with a floor area of about 11 meters by 16 meters, is made of sandstone masonry. The construction suggests that it was built in the 12th and 13th centuries. Presumably, an Alemannic timber-framed building was added to it in the 15th century. The six floors housed cellars, the great hall, kitchen, living quarters, and servant quarters. The largest room, now called the 'Knight's Hall,' is located on the second floor.
On the north side, the castle complex was protected by a wall with a battlement and two towers. The towers once served as a prison. While the western tower, called the 'Heaven' tower, had barred windows that looked out to the outside, the eastern tower, called the 'Hell' tower, had a 15-meter deep dungeon. The fortifications were connected to the city wall.
The Château de Chantilly comprises two attached buildings: the Petit Château built around 1560 for Anne de Montmorency, and the Grand Château, which was destroyed during the French Revolution and rebuilt in the 1870s. Owned by the Institut de France, the château houses the Musée Condé. It is one of the finest art galleries in France and is open to the public.
The estate"s connection with the Montmorency family began in 1484. The first mansion (now replaced by the Grand Château) was built in 1528–1531 for the Constable Anne de Montmorency by Pierre Chambiges. The Petit Château was also built for him, around 1560, probably by Jean Bullant. In 1632, after the death of Henri II, it passed to the Grand Condé who inherited it through his mother, Charlotte Marguerite de Montmorency.
Several interesting pieces of history are associated with the château during the 17th century.