Burg Beilstein, Medieval castle ruins in Greifenstein, Germany

Burg Beilstein is a castle ruin above the village of Beilstein in Greifenstein, Hesse, about 10 km southwest of Herborn. Its main surviving element is a 19.5-metre-high shield wall, three to four metres thick, on the south side of a residential building. A modern steel-and-glass structure now stands within the ruined Palas, whose historic footprint measured about 23 by 9 metres.

The lords of Beilstein are first documented in 1129, and the castle was probably begun then on the remains of an earlier destroyed fortification. Around 1226 the counts of Nassau took possession and displaced the Beilstein family, who moved their seat to Lichtenstein Castle. The counts of Nassau extended the castle, building the present Palas in the first half of the 14th century. In 1343 the line Nassau-Beilstein emerged and resided here until it died out in 1561; after the Thirty Years' War the complex decayed and was sold in 1812 for demolition.

Burg Beilstein is used today as a residential facility for people with disabilities, giving it a lived-in character that sets it apart from a typical museum. This everyday presence makes the medieval walls feel less like a relic and more like a place where life continues.

The ruin now houses a residential facility for people with disabilities, so only the outdoor areas can be visited. The building sits just a few metres above the village of Beilstein in the Ulmbach valley, about 10 km southwest of Herborn and 17 km northwest of Wetzlar. The preserved section is a steel-and-glass structure built inside the old Palas walls.

The castle's most striking surviving element is a Kemenatenbau, a residential wing whose south side retains a shield wall about 19.5 metres high and three to four metres thick. Two corner tourelles once reinforced the ends of the Palas, which measured roughly 23 by 9 metres and stood over 13 metres tall.