Hünenburg, Medieval castle ruins in Bad Pyrmont, Germany.

Hünenburg is the ruin of a hilltop castle on a spur of the Königsberg above Bad Pyrmont-Oesdorf, covering about 50 × 30 m. A ditch with an outer rampart encloses the site, with a gap in the south; in the east a motte holds a 9 × 9 m residential tower whose walls are only 80 cm thick, with a high entrance and slit windows. The tower was rebuilt in 1910 on the excavated masonry in the castle-romantic style of the time.

Hünenburg is not mentioned in any historical document, and its builders are unknown. Finds of pottery shards, knives, horseshoes, nails and sickles point to a foundation around 1100, with the castle expanding westward. It was probably destroyed by fire at the end of the 12th century. The site was excavated in 1910 by a history-minded citizen of Pyrmont together with Otto Weerth of Detmold.

The name Hünenburg refers to giants (Hünen) in local legend, not to the unknown builders, who are absent from all historical records. The tower visible today is a 1910 reconstruction on the excavated foundations, rebuilt in the castle-romantic style of the period. The site lies on a spur of the Königsberg above Oesdorf.

The ruins are located in a residential area of Bad Pyrmont-Oesdorf accessible via Oesbergstraße 33, where parking is available nearby. The site is well marked and provides good views of the fortification layout.

Excavations uncovered everyday objects that reveal the daily lives of castle inhabitants, including knives, horseshoes, nails, and sickles. These finds offer a rare glimpse into the material conditions of early medieval life.