Homburg sits on a hill above the village of Nümbrecht in the Oberbergischer Kreis, in the southeastern reach of the Bergisches Land. The written history begins in 1276, when Gottfried I of Sayn — head of a noble line from the House of Sponheim — transferred his castrum Homburg to King Rudolf of Habsburg in exchange for protection, then received it back as an imperial fief. That made the castle a Reichsherrschaft, an immediate imperial lordship answering directly to the emperor. The Counts of Homburg ruled from it. Their territory was small but legally significant — a tiny dot of sovereignty in a forested corner of the Rhineland, with the keep at its center.

By 1635, the line of Sayn-Wittgenstein held the castle, and Count Ernst von Sayn-Wittgenstein decided to modernize. The military fortress became a residence. Walls came down; windows went in; the keep was shortened and incorporated into living quarters; the courtyard was reworked for ceremonial entrances rather than defense. What you see at Homburg today is largely the result of his decisions in the 1630s and 1640s, with later baroque interventions adding the rest. The work was the kind of grand domestic statement Rhenish counts made in the seventeenth century to assert that they were minor royalty, not minor warlords. About a century later the property passed to the Sayn-Wittgenstein-Berleburg branch, who managed it with less interest. The castle slid into disrepair through the eighteenth and nineteenth centuries.

By 1900, Homburg was a melancholy ruin haunted by Sunday picnickers. Restoration began in 1904, slow and underfunded. The breakthrough came in 1926 when Hermann Conrad, a private collector, founded a museum in the castle. Conrad had assembled regional folk art, agricultural tools, ceramics, and household objects from the Bergisches Land — the kind of collection that captured what a vanishing rural culture looked like before electrification erased it. He installed his collection in the rooms of the castle and turned the building into something it had never been: a public institution dedicated to local memory. The Museum of the Oberbergisches Kreis grew out of his collection and still occupies the castle today.

In 2004, the Oberberg Biological Station and the German Forest Conservation Society added another layer to the site — a 2.8-kilometer nature trail looping out of the castle, through Homburg Bröl and Huppichteroth, past the Holstein Mill and the Dicke Steine boulder formation, and back. Nine information stations explain different parts of the landscape: an oak whose age is measured in tree rings, a tree-top platform that puts visitors at canopy height, a wooded section with a great spotted woodpecker nest viewable from the path, a section on hedgerow ecology. The Red House — the castle's old tithe barn — became the headquarters of the biological station. The combination is unusual: a museum of regional history and a working ecological research center inside the same medieval complex.

Walk through Homburg today and you cross at least three different castles inhabiting the same footprint. The eleventh-century keep, discovered in 1999, lies beneath your feet — its diameter mapped, its function military. Around you stretches the seventeenth-century residence Ernst von Sayn-Wittgenstein imagined, with baroque facades and ornamental courtyards. And on the wall of every other room hangs something from Hermann Conrad's twentieth-century vision of what regional memory should look like — a wooden plow, a Bergisch ceramic, a stamped tin coffee can. The castle is small enough to walk through in an hour. The history is long enough to take longer than that to absorb.