To be privately owned
Luisenburg Castle (Mannenbach)

Louisenburg Castle, a structure in the canton of Thurgau, Switzerland, is on Lake Untersee in Mannenbach. Built in the 19th century, it is an example of architecture from that period.
History+
The origins of Louisenburg Castle date back to 1834, when the former French Brigadier General Marquis de Crenay had a new manor house built on the site of a former chaplaincy building. He named it after Louise de Séréville, his wife's niece. In 1873, the estate changed hands and was acquired by Jean Bürgi-Betschaft. Just five years later, in 1878, it passed to Cantonal Councillor Abraham Fehr-Häberlin. Baroness Emilie von Breidenbach was the owner from 1889, followed by Jean Kaestlin in 1906. After 1945, it belonged to Mrs. ten Brink-Merian, before returning to the possession of the Kaestlin family in 1960, who still own it today.
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: 47.6718, 9.0485