Ehrenfels Castle was (re-)built about 1212 at the behest of the Archbishop of Mainz as a defensive work against the constant attacks by Elector Palatine Henry V, who, as Imperial vicar of Franconia, strived to cut down the archbishop's reach. Mainz staffed the castle with Burgmannen and erected a customs post controlling the shipping on the Rhine, supplemented by the Mouse Tower below at the river. Heavily damaged in the course of the Thirty Years' War, the castle was finally devastated by French troops under the command of Lieutenant General Nicolas Chalon du Bléduring the 1689 Siege of Mainz.
The ruin can be reached from Rüdesheim via a hiking trail through the vineyards. The interior however can only be visited in guided tours by prior appointment.
References:Rosenborg Palace was built in the period 1606-34 as Christian IV’s summerhouse just outside the ramparts of Copenhagen. Christian IV was very fond of the palace and often stayed at the castle when he resided in Copenhagen, and it was here that he died in 1648. After his death, the palace passed to his son King Frederik III, who together with his queen, Sophie Amalie, carried out several types of modernisation.
The last king who used the place as a residence was Frederik IV, and around 1720, Rosenborg was abandoned in favor of Frederiksborg Palace.Through the 1700s, considerable art treasures were collected at Rosenborg Castle, among other things items from the estates of deceased royalty and from Christiansborg after the fire there in 1794.
Soon the idea of a museum arose, and that was realised in 1833, which is The Royal Danish Collection’s official year of establishment.