[1] The castle was built around 1020 by Count Radbot, of the nearby county of Klettgau in the Duchy of Swabia, and Werner, Bishop of Strasbourg.
[2] They had the castle erected 35 km southwest of Klettgau, on the Aar, the largest tributary of the High Rhine.
It is believed that he named the castle after a hawk (German: Habicht) seen sitting on its walls.
[3] The name of "Habsburg" was not added to the noble title until Radbot's grandson, Otto II.
[3] Habsburg Castle's importance diminished after Radbot's seventh generation descendant Rudolph moved the family's power base to Austria in 1276.