Hollenfels Castle (Luxembourgish: Buerg Huelmes; French: Château de Hollenfels; German: Burg Hollenfels), with a history dating back to the 11th century, is one of the castles located close to the River Eisch in the Valley of the Seven Castles in central Luxembourg. Today it is used as a centre for activities for young people, including a nearby youth hostel.[1]