On 19 and 20 September 2026, the Journées du Patrimoine Heritage Days return to Île-de-France with a simple idea: give the public a chance to discover places that keep the region’s heritage alive, whether historic, cultural, or a bit offbeat. In the Val-de-Marne, the Domaine de Grosbois is among those standout sites. Behind the gates of its vast grounds lies Europe’s largest trotting-horse training center.
The story of Grosbois goes back long before the horse races. Its 17th‑century château and wooded grounds have passed through the hands of several illustrious families, including Marshal Berthier, Napoleon’s trusted ally. In 1962, the site was bought by the Société du Trotteur Français to establish a training center able to accommodate the horses that compete in the major events at the Paris-Vincennes Hippodrome. This renewed vocation has helped preserve the estate and open a new chapter in its history.
Today the estate covers more than 400 hectares and can accommodate up to 1,500 horses during the winter meeting. Each morning, dozens of trotting horses train on the various tracks, flanked by their trainers, their drivers and a whole team of professionals. With its stables, its Trotting Museum, its documentation center and numerous facilities, Grosbois is at once a workplace, a hub of knowledge transfer and a guardian of French horseracing heritage.
Heritage Days offer a rare behind-the-scenes look. Beyond the château, visitors can gain a clearer sense of how racehorses are trained, the trades that surround them, and why this estate plays a crucial role in the world of trotting. It’s also a way to discover a heritage that’s often overlooked, just a few kilometers from Paris.
A guided tour of a horse-training facility
Go behind the scenes of the grandest trotting races, the heart of Paris-Vincennes’ racecourse.
Regarded as trotting’s paradise, the Grosbois training centre for Standardbreds sits barely a 15-kilometre drive from the Paris-Vincennes track. This 400-hectare site boasts top-tier facilities dedicated to daily training of trotters and can accommodate up to 1,500 horses during the winter meeting.
Come and enjoy this exceptional site with friends or family. This one-hour guided tour into the very core of harness racing will let you discover the main training infrastructures, such as the tracks and the riding hall, as well as catch a glimpse of private spaces like the stables and the veterinary clinic.
About a 2 km route: please wear sturdy shoes and weather-appropriate clothing (umbrella not allowed).
Participation conditions: Discounted price: €10. Youth rate: €5 (under 12) - Booking required | Special rate - 01 49 77 15 22, https://f.dlt.letrot.com/f/lp/grosbois-visite/up1nqjn4
Schedule: Saturday, September 19, 2026 — 10:30 to 11:30
A close-up on Grosbois's tiny creatures
The Natural History Photography Society is hosting a large-format exhibition in the castle’s moat.
Fourteen shots by Alain Champagne and Francis Robeyns illuminate a world that is as fascinating as it is often overlooked: the tiny creatures that pollinate, decompose, and form essential links in the food chain. Their shared eye for observation, sharpened by macro photography, brings to light details invisible to the naked eye: the delicate wings of a butterfly, the iridescent sheen of a beetle, and the intricate structure of a dragonfly’s eyes. They remind us that safeguarding biodiversity begins with wonder and understanding.
Participation requirements: Free - Free | No reservation required
Hours: Saturday, September 19, 2026 — 11:00 AM to 5:00 PM
Self-guided tour of the Trotting Museum
Since 2010, the château has also housed a small museum dedicated to the history of this equestrian discipline, trotting.
It opens with the origins of harness racing, recalling the Olympiads, ancient chariot races and the Circus Maximus, then traces the history of trotting races in France from their 19th‑century beginnings to today, presented in a modern and engaging way.
While the museum shines a light on the men and horses who wrote trotting’s history, it also explores the architecture of the great racecourses, the evolution of harnesses and tack, and the breeding and improvement of the horse breed.
You are free to wander through the museum, reading the informational texts or listening to the audio guide on your smartphone. For younger visitors, a family‑friendly activity booklet is available at the ticket desk, allowing families to explore the museum while having fun.
Participation conditions: Free - Free | Reservations required - 01 49 77 15 22, https://f.dlt.letrot.com/f/lp/grosbois-visite/up1nqjn4
Schedule: Saturday, September 19, 2026 — 11:00 a.m. to 5:00 p.m.
Grosbois Forest Festival
This year, Domaine de Grosbois invites the public to discover its natural and forest heritage, as it proudly hosts the “Forest Festival” led by the Val-de-Marne Department with the collaboration of all signatories of the Arc Boisé Charter.
The event will feature a wide range of activities designed to raise awareness of the richness of wooded spaces for all ages: hikes, beekeeping workshop, model boating, tree climbing, photo exhibition, creative workshop, guided tours, and an activity passport to encourage participants to take on more challenges, workshops, and encounters.
A picnic lunch will add a convivial, bucolic touch to the day. You can bring your own picnic or enjoy a menu crafted especially for the event, featuring forest-derived products. Two food trucks will be on site to spark your taste buds.
Participation conditions: Free park access for all – Free
Hours: Saturday, September 19, 2026, 11:00 a.m.–5:00 p.m.
Passport: become a guardian of the Grosbois forest!
To challenge visitors, the Domaine de Grosbois offers an activity trail with a passport to fill out, centered on the theme of the forest festival. The aim is to discover the domaine’s natural and cultural heritage while having fun.
At each activity and booth you visit, a stamp will be placed in the passport; once it’s complete, participants can pick up their Domaine de Grosbois badge and will officially become guardians of the Grosbois forest.
On the program: tree climbing, beekeeping workshop (11:00–14:30), castle tours, photographic exhibitions on the little creatures of Grosbois, an introduction to fishing, guided forest walks in the Grosbois woods, and various creative workshops at the stands offered by the Val-de-Marne department.
Entry requirements: Free | No reservation required
Hours : Saturday, September 19, 2026 – 11:00 AM to 5:00 PM
Costumed tour of the Wagram Princes' Residence
Step into the intimate world of a family home, the countryside residence of the Princes of Wagram, and experience history as if you were living it.
Dressed in their finest costumes, the members of the Boissy-Saint-Léger Historical Circle invite you on a theatrical stroll through the castle. Page by page, they’ll illuminate the major chapters of its past. From the Louis XIII dining room with its 17th‑century wall paintings to the Restoration-era library built for the son of Marshal Berthier around 1838, you’ll trace more than four centuries of French history.
Participation conditions: Reduced fare: €10. Youth fare (under 12): €5. Reservations required | Special rate: 01 49 77 15 22, https://f.dlt.letrot.com/f/lp/grosbois-visite/up1nqjn4
Times: Saturday, September 19, 2026 – 11:45 AM to 1:00 PM
The Grosbois Castle, at your own pace
Come visit Grosbois Castle at your own pace, with a self-guided booklet or audio commentaries you can download to your smartphone.
You will move from salon to salon through more than four centuries of French history, from Henry IV to the present day. Costumed figures will bring your visit to life and spirit you to another era.
Built in the early 17th century, the castle has passed through a succession of owners, from Nicolas de Harlay, Henri IV's minister, to the Delcendants of Marshal of the Empire Alexandre Berthier. Fully furnished, it preserves a large part of the Napoleonic-era heritage: chairs, paintings, and various decor. It also houses a rare 17th-century remnant—the original decoration of the Louis XIII dining room, comprised of exceptional wall paintings. The castle’s library, laid out by Berthier’s son during the Restoration, gathers more than 3,000 military, scientific and historical works, as well as maps and unpublished battle plans.
Grosbois Castle has been listed as a historic monument since 1948. Since 1962 it has belonged to the Society for the Encouragement of French Horse Breeding, which safeguards and promotes this exceptional heritage.
Participation conditions: Reduced fare: €5 | Youth rate (under 12): €0 — Special pricing | Reservations required - https://f.dlt.letrot.com/f/lp/grosbois-visite/up1nqjn4
Schedule: Saturday, September 19, 2026 — 2:00 PM to 5:00 PM
Walking tour: "We are the cousins of the trees"
What if trees were so much more than our neighbors? What if, all along, they were distant cousins, sharing with us a common story of life?
The association Les Champs des Possibles invites you on a roughly 75-minute stroll to slow down, observe, and reconnect with the forest.
As we walk, we’ll discover the surprising kinship that binds us to the trees: we breathe thanks to them, we share the same elements and cycles, and like them, we depend on the richness of the soil and the diversity of life.
We’ll pause to take in what makes a forest: not only the trees, but also the plants, insects, fungi, and a myriad of invisible micro-organisms weaving the links of a thriving ecosystem beneath our feet.
If conditions permit, we’ll explore a patch of forest soil together: we’ll smell it, feel its texture, examine its minerals, organic matter, and the quiet life that makes it a miniature world.
Registration is free on-site at the Walks stand.
Suitable for anyone able to stand (whether walking or remaining stationary) for 1h15 to 1h30 — recommended ages from 8 to 80.
Participation conditions : 25-30 people - Free | No reservation required
Schedule: Saturday, September 19, 2026 — 2:00 PM–3:30 PM, 3:45 PM–5:00 PM
A Measured Stroll
A woodland stroll led by storyteller-musician Dominique Motte.
Let yourself be guided along the Grosbois estate trails on a 90-minute walk filled with stories, legends and nature-inspired tales. At each stop, the forest reveals some of its secrets, remarkable trees bear witness to bygone centuries, leaves rustle in the wind, and nature itself tells its story. Young and old are invited to slow down, take their time, and listen with wide ears and vivid imaginations. Accompanied by a guitar, the storyteller’s voice resonates with the surrounding nature. From clearings to stands of trees, tales from around the world come to life, weaving mystery, poetry and humor into an exceptional setting.
Family-friendly and multi-generational (ages 5 to 105).
Easy walk (please wear suitable footwear and clothing that covers you).
Conditions de participation : Limited to 20–25 participants (free on-site registration at the Walks stand) - Free | No reservation required
Schedule: Saturday, September 19, 2026 — 2:00 PM to 3:30 PM
The Grosbois Forest Through the Ages
A conference organized by Roger Guillemard on safeguarding the Notre-Dame forest.
The Grosbois, La Grange, Camaldules and Piple woodlands form a single forest massif—the Notre-Dame Forest—spanning more than 3,000 hectares. This forest has been exploited since the twelfth century: timber is essential for building and heating. The clayey soil required an extensive network of ditches feeding streams, ponds and pools. Clay, sand and meulière stone are quarried here. Farms and tile works grew up around the forest, as did residential developments, at the forest’s expense. It is also a major hunting reserve. How has this important wooded heritage—frequently threatened by real estate projects—been preserved up to the creation of the Arc Boisé in 2004?
Conditions de participation : 25-30 participants - Free | No reservation required
Schedule: Saturday, September 19, 2026, 2:00 PM–3:00 PM
Forest and landscape stroll
The surrounding landscape is the result of a long history, shaped as much by nature as by human activity. On this stroll through the Domaine de Grosbois, we will learn to observe the paths, the woods, the meadows, the hedges and the viewpoints that make up this territory with fresh eyes.
Through short observation stops and conversations, we will discover how the relief, the vegetation, human activities and the estate’s history have shaped the landscapes of yesterday and today. This walk will also be an opportunity to better understand the challenges of preserving and enhancing this natural and cultural heritage.
One-hour visit - sturdy walking shoes, a hat and clothing that covers.
Free registration on site at the Balades stand.
Participation requirements: Limited to 25–30 people maximum - Free | No reservation required
Schedule: Saturday, September 19, 2026 - 2:30 PM ⤏ 3:30 PM, 4:00 PM ⤏ 5:00 PM
A sensory and birdwatching stroll
On the occasion of the Forest Festival, explore the natural riches of the Domaine de Grosbois during a birdwatching stroll led by the Objectif Terre association.
During this walk, learn to identify the birds that inhabit the estate by their songs, silhouettes, and behaviors. This outing, open to everyone, will help you understand the role these species play in ecosystems and the importance of preserving their habitat.
Whether you're a nature enthusiast, a photography buff, or simply curious, this stroll offers a fresh perspective on the Domaine de Grosbois's exceptional natural heritage.
Bring sturdy walking shoes and, if you have them, a pair of binoculars.
Free on-site registration at the walks stand.
Participation conditions: 25 people maximum - Free | No reservation required
Schedule: Saturday, September 19, 2026 — 4:00 PM to 5:00 PM
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Dates and Opening Time
From September 19, 2026 to September 20, 2026
Location
Domaine de Grosbois
46 Avenue de Grosbois
94440 Marolles en Brie
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