Isenburg

Germany, Germany

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Isenburg refers to multiple castles and ruins across Germany tied to the historic Counts of Isenburg, with prominent examples including the Renaissance Schloss Isenburg in Offenbach am Main, Hesse—a 16th-century red-brick palace rebuilt after a 1564 fire, once home to Swedish King Gustavus Adolphus during the Thirty Years' War and now housing a design university.

In Rhineland-Palatinate near Hatzenport, the medieval Isenburg Castle (Stammburg), built around 1100 as a shared Ganerbenburg for family branches, was abandoned by the 17th century and survives as an atmospheric ruin overlooking the Moselle.

Other sites like the 12th-century spur castle ruins above Hartenstein in Saxony and the overgrown medieval fortress near Essen in the Ruhr highlight the name's recurring legacy in fortifications from the Holy Roman Empire era.