Parc D'En Haut

Parc d'En Haut is a wooded area in the commune of Saint-Léger-en-Yvelines, set in the heart of the Forest of Rambouillet, roughly halfway between Montfort-l'Amaury and Rambouillet in the Yvelines department. The name carries a layered history: the land once formed part of a larger estate that included a château, the neighboring Parc d'En Bas, a stud farm known as the Harasserie, and surrounding farms and mills. In the 16th century, Count André de Foix established a notable horse-breeding operation here, run under what was known as the Châtellerie de Saint-Léger. After Louis XIV ordered the château's demolition in 1667, the stud farm itself was relocated in 1715, and the site gradually shifted from a residential estate into forested and managed land.

What is at Parc d'En Haut today?

Today, the former estate grounds host the headquarters of Cerf78, a research center dedicated to studying the Rambouillet forest and its deer population. From this base, researchers monitor wildlife and track the ecological condition of the Forest of Rambouillet, one of the largest forested areas in the Île-de-France region west of Paris.

Why does this area matter for nature conservation?

Parc d'En Haut borders the Réserve biologique dirigée (directed biological reserve) of the Forest of Rambouillet, whose surface area was doubled by ministerial order in 2021, growing from 576 to 1,152 hectares. The reserve is split into 19 zones of significant ecological value, and it is managed by the National Forestry Office (ONF) under stricter protective rules than the surrounding forest: cataloguing species of heritage value, limiting interventions during breeding and growing seasons, controlling artificial lighting, and combating invasive plant and animal species. The Forest of Rambouillet stands out for its ecological richness, home to around fifty remarkable plant species alongside bats, insects, amphibians, open-habitat birds, and reptiles. Within the reserve, fishing is banned, as is introducing non-native species or flying drones, and visitors are discouraged from leaving the marked trails.

What hiking trails pass through Parc d'En Haut?

The Réserve biologique dirigée du Parc d'en Haut serves as the starting point for one of the area's most popular hiking routes, a loop of around 15 kilometers that passes near the Rompu Pond and a tree known as the Ascension Oak. The trail winds through varied sections of forest, combining scenic value with opportunities to observe local wildlife, and is a common choice for visitors exploring the Forest of Rambouillet and the area around Saint-Léger-en-Yvelines.

Frequently asked questions

Can you go for a walk or bike ride at Parc d'En Haut? Yes, marked hiking trails run through and around the area, including a popular roughly 15-km loop, though within the biological reserve itself visitors are encouraged to stay on the designated paths.

Is Parc d'En Haut an urban-style park with paths and benches? No — it is really the historic name of a forested area, a former part of a landed estate, that today functions as a natural and forestry site housing the Cerf78 research center rather than a landscaped city park.

What used to be located here? The site was once part of a larger estate that included a château and a horse-breeding stud founded by Count André de Foix; the château was demolished on the orders of Louis XIV in 1667.