To be privately owned
Torre Fiorenzana Castle (Grono)

In Grono in the Swiss canton of Graubünden stands Torre Fiorenzana Castle. This residential tower, originally belonging to a family, holds dramatic events within its ancient walls.
History+
The origins of Torre Fiorenzana Castle date back to the late 12th century, when it was built for the Sacco family. The construction served as a five-story residential tower with a rectangular footprint. A dark chapter in its history occurred in 1406, when Alberto de Sacco was murdered within the castle walls. In 1977, a comprehensive restoration of the structure took place.
Source: Wikipedia · Licence: CC BY-SA 4.0
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: 46.2502, 9.1502