Castle Eyneburg, Medieval castle in Hergenrath, Belgium

Castle Eyneburg is a multi-part stone castle complex on a hill above the left bank of the Göhl near Hergenrath, in Kelmis, Belgium. Its core is a large round bergfried of layered rubble stone, three storeys high, with a modern oriel on the northwest side and a narrow arrow slit to the west; a conical roof crowns a small added timber-framed storey. A tall gabled hall with a steep slate roof, a slender octagonal spire and a large pointed-arch traceried window adjoins lower wings, one with a tiled roof and dormers, another with pointed-arch openings and a chimney. A chapel and a farmyard complete the walled complex.

The fortress was first mentioned in written records in 1260, built to protect the nearby Galmeiberg mining operations that were economically important for the region. A serious fire in 1640 left lasting damage that permanently changed the look of the structure.

Locals also call the castle Emmaburg, after a legend that Emma, said to be a daughter of Charlemagne, lived here with her lover Einhard. The story is carved on the well in the courtyard, where a woman is shown carrying a man on her back. The castle has been closed to the public since 2011.

The castle has been closed to the public since 2011, so visits are limited to viewing the complex from outside its walls. It stands on a wooded hill edge above the Geul valley, about one kilometre southwest of Hergenrath's bell tower. The grounds and park are enclosed by walls, so there is no access to the courtyard or the chapel.

In the late 1800s, cloth manufacturer Theodor Nellessen filled the interior with a large collection of antique furniture and art objects that he had gathered himself. This turned a former military fortress into a private home with the feel of a manor house.