Stolzenfels Castle is a former, medieval fortress castle ("Burg") turned into a palace, near Koblenz on the left bank of the Rhine, in the state of Rhineland-Palatinate, Germany. Stolzenfels was a ruined 13th-century castle, gifted to the Prussian Crownprince, Frederick William in 1823. He had it rebuilt as a 19th-century palace in Gothic Revival style. Today, it is part of the UNESCO World Heritage Site Upper Middle Rhine Valley.