Schloss Therasburg, Medieval castle in Sigmundsherberg, Austria

Schloss Therasburg is a medieval castle set on a ridge above the Therasburger stream in Sigmundsherberg. The structure features defensive walls combined with a sandstone entrance portal and stone bridge that serves as the main approach.

The castle was built around 1320 and first documented in 1327 under the ownership of Ortlieb Zvendel von Teraczpurch. Over the following centuries it passed through different hands and underwent modifications while maintaining its defensive character.

The name Therasburg derives from the 1327 form Teraczpurch, recorded for Ortlieb Zvendel. In 1473 the castle served the robber knight Kratzer as a base for raids on the nearby Rittsteig. A local landmark is the Kaudelka larch in the Therasburger valley, named after the estate's administrator, who in 1876 harvested 3.8 kg of soybeans from 300 yellow seeds.

The castle sits at 437 meters elevation and access varies seasonally, so checking in advance is important. Sturdy footwear is recommended as the approach involves some uphill terrain and uneven surfaces.

During World War II, Schloss Therasburg stored holdings of the University of Vienna Library, alongside works from the catalogue room of the Austrian National Library; the remaining books were split among eight other sites. The same role was played by Schloss Horn, Schloss Rosenburg and more than ten other locations.