Alt-Regensberg Castle was built about the mid-11th century AD by the House of Regensberg in the municipality of Regensdorf. The decline in importance of the castle had been shown already in the Old Zürich War, when Zürich's opponent Alt-Regensberg occupied without resistance. Later the ruins served as a quarry.
The quadratic keep dates from the first construction phase. The exterior of the residential tower has been transformed remarkably over the years. The outer casing of the 11th-century structure was filled with boll stones and mounted in horizontal mortar joints strokes. By 1200 the entire outer surface was chipped away and replaced with carefully edited boss squares. The whole tower thus received a much more upmarket appearance.
In the northern part of the complex is a rectangular foundation wall leaning against the perimeter wall. Here arose in the 12th or early 13th century wooden buildings that served as stables and outbuildings. They were moved to the south and replaced by a palas in the course of the 14th century claimed the whole area between keep and circular wall in the northeastern area.References:
Bouillon Castle was mentioned first in 988, but there has been a castle on the same site for a much longer time. The castle is situated on a rocky spur of land within a sharp bend of the Semois River.
In 1082, Bouillon Castle was inherited by Godfrey of Bouillon, who sold it to Otbert, Bishop of Liège in order to finance the First Crusade. The castle was later fitted for heavy artillery by Vauban, Louis XIV's military architect in the late 17th century.
The castle is entered over three drawbridges. The main courtyard then leads to the ducal palace with its 13th century Salle Godefroy de Bouillon. From there visitors climb up to the top of the 16th century Tour d’Autriche for a breathtaking panorama of the town and river, before they way back via the torture chamber, citerns and dungeons, and past the 65m deep well Shaft.