To be privately owned
Küçüksu Palace

In Istanbul, the Küçüksu Palace, a residence made of white marble, is located directly on the Bosphorus. Originally designed as an Ottoman excursion palace, it served the sultans as a daytime retreat.
History+
The Küçüksu Palace was built as an excursion palace for the sultans, who came here to spend the day but always returned to their main residences before nightfall. For this reason, the palace has no bedrooms. For many decades, the area around the palace was a picnic spot for the local population, until the construction of the first Bosphorus Bridge claimed the meadows as an assembly area for bridge components.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Daniel Pelletier
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: 41.0784, 29.0649