The remains of the Castle can be visited
Osterburg Castle

Osterburg Castle Ruin, a former hilltop castle, is situated on a triangular rock plateau in the cadastral community of Haunoldstein-Osterburg in the St. Pölten Land district of Lower Austria. Its location, steeply sloping southwards into the Pielach Gorge, provided a natural defense.
History+
The castle's origins date back to the late 12th century, with the builders remaining unknown. Around 1200, it was owned by the Counts of Peilstein. In the 13th century, Osterburg became a territorial fief and was inhabited by followers of the Häusler family. Through marriage, it passed to Konrad Eisenbeutel in the early 14th century, and later inherited by the Tursen von Tiernstein. Rudolf Turso von Tiernstein had the castle expanded in 1405. After further changes of ownership, including the Prüschenk brothers, Emperor Maximilian I enfeoffed Knight Hans Geyer with the castle in 1514. The Geyer family modernized the complex and acquired a regional court.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.wehrbauten.at/noe/niederoesterreich.html
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 48.2052, 15.4411