Burg Sonnenberg, Medieval castle in Sonnenberg, Germany

Burg Sonnenberg is a castle ruin on a rock spur above Wiesbaden-Sonnenberg, begun around 1200 by the Nassau counts Henry II and Rupert IV against the Lords of Eppstein. Its 1208 bergfried now houses a museum and has a roofed viewing platform; the upper castle was expanded between 1221 and 1242, and the lower castle was added after 1298. Three entrances remain, including the main tower to the east and former town gates in the valley.

The castle was built in the early 13th century by the Nassau counts Henry II and Robert IV as a defensive post against the Lords of Eppstein. Over time it lost its military role and gradually fell into the state it is in today.

The tower holds a small display of objects from the medieval period, including items tied to the time when Nassau controlled the region. Walking through the remaining walls gives a clear sense of how a hilltop fortress was arranged and used.

Marked paths lead from the center of Sonnenberg up to the castle, though the ascent is steep in places and the ground is uneven. Sturdy shoes are a good idea, and visitors with mobility difficulties should be aware that the site is not wheelchair accessible.

In 1298, after Adolf's death, the Eppsteiners and the Archbishop of Mainz captured and devastated the castle; Adolf's young son Gerlach was saved. Gerlach later reconciled with the former enemies and expanded the castle, beginning its most important period. Emperor Louis the Bavarian visited in 1338.