The Castle can't be visited
Leopoldsberg Castle
The Castle on Leopoldsberg, originally known as Kahlenberg Castle, served the Babenbergs and the Habsburgs as a strategic point above the Danube.
History+
The castle's origins date back to the 12th century. After the Habsburgs took over the complex, its decline began in 1377 with the expansion of Laxenburg Castle. In 1529, the castle was likely blown up during the First Ottoman Siege. Around 1679, a new chapel was built on the plateau. Emperor Charles VI commissioned a castle to be built next to St. Leopold's Chapel around 1720, based on designs by Antonio Beduzzi. The last remnants of the medieval castle were removed in 1786.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Leopoldsbergburg_Loggia.JPG
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: 48.2781, 16.3466