Burg Frauenberg, Medieval castle ruin in Grisons, Switzerland

Burg Frauenberg is a ruin on the Plontabuora hill at 1205 m above sea level, southwest of Ruschein in the Surselva. What remains is a rectangular walled enclosure of about 21 by 16.5 metres, built throughout in opus spicatum, with walls around 1.5 metres thick and a gate in the northwest wall whose jambs have been removed. A 2013/2014 survey suggested a timber structure stood on the walled square rather than a roofed defensive castle.

The castle was the seat of the Lords of Frauenberg, a family first documented in 1257, probably a branch of the Barons of Sagogn. Its best-known member, Heinrich II (recorded 1284–1305), was a minnesinger and moved his residence to Gutenberg Castle in Liechtenstein in 1290. Through his daughters the ruin passed to the Werdenberg family, and from the 15th century its stones were quarried for other buildings.

The name Frauenberg probably comes from the Sagogn branch that split around 1250; the castle is first documented in 1257 with Heinrich von Frauenberg. The false name Frundsberg stems from chronicler Ulrich Campell after 1570, who misread the name as the ancestral seat of Georg von Frundsberg. The castle is mentioned only once in a document, in a Pfäfers urbarium around 1450.

You can reach the ruins by following marked hiking trails from a nearby parking area. Information panels along the way help you understand the structure and what you are seeing.

The name Frundsberg, sometimes used for the ruin, comes from the chronicler Ulrich Campell after 1570, who read the castle's name as the ancestral seat of the Landsknecht leader Georg von Frundsberg. The theory is now rejected and seems to rest on a misreading; Frundsberg's castle was in Mindelheim, and he lived in southern Bavaria.