The Château de Voisins near Rambouillet, outside Paris, will become a luxury hotel with golf and spa

Built between 1903 and 1906 in Saint-Hilarion, in the Yvelines, between Rambouillet and Épernon, the Château de Voisins is the subject of a plan to turn it into a luxury hotel with a spa and golf course. According to the mayor, Antoine Giacomotto, quoted by the local press on 23 October 2026, it will have around 110 rooms, backed by more than 300 million euros of investment. But nothing is settled yet: no investor, no brand and no planning permission have been made public, and the hotel will not open before around 2030.

☰Contents

1. 110 rooms and a golf course, says the mayor
2. Saint-Hilarion’s unanimous vote in 2025
3. When will the hotel open?
4. Investor, brand, water: the open questions
5. One of the last great French châteaux
6. The park in colour, photographed in 1927

110 rooms and a golf course, says the mayor

The mayor of Saint-Hilarion put figures on the project at the 25th anniversary of the Syndicat d’énergie des Yvelines, the local energy authority, held at the château itself. According to the local press, he described “a prestige hotel with almost 110 rooms, the recreation of the original golf course, and the creation of a spa and several restaurants”. More than 300 million euros will be invested and 300 jobs created; the mayor sees it as “a fifth luxury hotel” for the Yvelines.

The rooms will be spread between the château and new buildings, including standalone lodges, with staff housing on site. A central kitchen and a building for the teams have also been mentioned in Gazeran. The former dining room will become a restaurant, and hunting will continue in the surrounding woods. These figures remain verbal announcements: an earlier estimate, raised in Gazeran, spoke of around 250 million euros and 400 jobs.

Saint-Hilarion’s unanimous vote in 2025

The project rests first of all on official decisions. On 25 September 2025, Saint-Hilarion’s municipal council unanimously passed resolution no. 35-2025. It launches a “déclaration de projet”, a procedure that allows the local urban plan (PLU), the document that sets what may be built, to be amended “for a project to restore and enhance the Domaine de Voisins, in order to develop hotel and leisure activities there”.

Three months earlier, on 24 June 2025, the commune had applied a higher rate of development tax, the levy due on new construction, to the area (13 votes for, 1 abstention), a decision corrected on 25 September. In Gazeran, home to part of the estate, the municipal council meeting of 29 June 2026 confirmed the plan for a “luxury hotel with spa and golf”, which requires a complete renovation and an extension. Saint-Hilarion’s resolutions can be consulted on the town hall website.

When will the hotel open?

The Gazeran minutes set out the planned timeline: a public meeting in the autumn, a public inquiry in December 2026 or January 2027, then works from the third quarter of 2027, lasting three to four years. The hotel will therefore not open before around 2030.

In his autumn 2026 letter, the mayor, Antoine Giacomotto, told residents about an information document and a public meeting on the “project to restore the Domaine de Voisins”. According to the local press, two public meetings will be held in early November 2026, one in Gazeran, the other in Saint-Hilarion.

Investor, brand, water: the open questions

The funding is private, but the identity of the investors has not been made public. No hotel operator or brand has been announced, and no planning permission is known to date. Star ratings are only awarded after opening, so nothing yet points to a five-star hotel.

Then there is the water. Gazeran’s municipal council notes that water supply and sewerage, both their cost and who will pay for them, have yet to be settled. A borehole, led by the Rambouillet Territoires intercommunal authority, is being considered as an option; the developers will only fund the volumes linked to the estate. The mayor insists his council is “extremely vigilant and demanding, particularly on environmental matters”. Château conversions like this take time, as shown by the hotel project at the Château de Divonne-les-Bains, set back by a fire.

One of the last great French châteaux

The château was built from 1903 to 1906 by the architect René Sergent for Count Edmond de Fels, modelled on the Château de Saint-Hubert, designed by the architect Gabriel. It is one of the last great châteaux built in France, and has been partly listed as a historic monument since an order of 30 December 1983.

The estate covers 230 to 250 hectares, depending on the source, with an ornamental lake fed by the Guéville, a small river. To stay in the area right now, Le Barn, in the Rambouillet forest, features in our All Saints’ holiday selection; further north, you can sleep at the foot of the Palace of Versailles at Airelles Le Grand Contrôle.

The park in colour, photographed in 1927

The formal French gardens are the work of the landscape architects Henri and Achille Duchêne, who worked on them from 1903 to 1929. In 1927, the camera operators Roger Dumas and Georges Chevalier photographed them in colour on autochrome plates, one of the earliest colour photography processes, for the Archives de la Planète, a collection held by the Musée départemental Albert-Kahn.

These images show the main courtyard, the salons and the park as they were then: embroidered parterres, those beds clipped into arabesques, the great pool and its statues, and the ornamental lake reflecting the façade. It is this setting that the project intends to restore, original golf course included.