Did you know that a genuine bustling trading city of several thousand inhabitants lay hidden beneath the fields and copses of the Neauphle plain? The Journées du Patrimoine 2026 will be back in Paris and across the entire Île-de-France on 19 et 20 septembre 2026 to fling wide open the doors to our region’s lesser-known treasures. It’s the chance to ditch the urban pavement for a foray toward Jouars-Pontchartrain, in the Yvelines, where the site de la Ferme d'Ithe unveils centuries of archaeology and buried legends.
The Ferme d'Ithe site sits at the heart of the ancient settlement of Diodurum, a Gaulish name that evokes either “the city of the gods” or the “divine market.” Set along the great Roman road that linked Lutetia (Paris) to Cenabum (Orléans) and Dreux, the town housed sanctuaries, baths, artisan workshops, and a vast Gallo-Roman theatre whose foundations still yield new clues for archaeologists. Local accounts even suggest that tunnels from the former agricultural workings may have connected to ritual galleries hidden beneath the plain, a mystery that continues to intrigue visitors and history enthusiasts alike.
Beyond its Gallo-Roman underground, the Ferme d'Ithe stands as a striking record of continuous occupation across the centuries. Transformed into a Cistercian barn and then allied with the Templar orders in the Middle Ages, the property still features stone meulière and limestone farm buildings typical of the Paris Basin, flanked by medieval and modern outbuildings. The association that runs and promotes the site today is committed to safeguarding this dual identity: a well-preserved rural estate and an open-air archaeological ground.
Want to uncover the secrets of the builders of Antiquity and plan your on-site visit? Discover the full program of festivities and activities below:
Fibula-Making Workshop
Join us to explore the history of fibulae and walk away with your own handmade creation!
Participation requirements: Free | No reservation required
Hours : Saturday, September 19, 2026 — 2:00 PM to 6:00 PM | Sunday, September 20, 2026 — 10:00 AM to 1:00 PM, 2:00 PM to 6:00 PM
Experimental archaeology workshop
Reconstruction of a Gallo-Roman potter's kiln with firing up, loading, and firing of ceramics on Saturday. Unloading on Sunday afternoon.
Participation terms: Free | No reservation required
Hours: Saturday, September 19, 2026 — 2:00 PM to 6:00 PM | Sunday, September 20, 2026 — 10:00 AM to 1:00 PM, 2:00 PM to 6:00 PM
Kids' discovery workshop: exploring the profession of a ceramologist
You’re keen to dip into the study of archaeological pottery? Step into the shoes of an archaeologist/ceramologist for a day. An itinerant laboratory* in partnership with Inrap: reconstruction, drawing, analysis… the steps of an investigation that reveal the work of an archaeology expert.
From 6 years old.
*Coproduction Cap'Archéo-Cap Sciences / Inrap, with the support of the Fondation EDF
Participation requirements: Free | No booking required
Hours: Saturday, 19 September 2026 – 14:00 ⤏ 18:00 | Sunday, 20 September 2026 – 10:00 ⤏ 13:00, 14:00 ⤏ 18:00
Weaving Workshop
Try your hand at weaving in a hands-on workshop and discover how, long before modern machines, people crafted fabrics, clothing, and accessories by hand on a loom.
How to participate: Free | No reservation required
Hours: Saturday, September 19, 2026 — 2:00 PM to 6:00 PM | Sunday, September 20, 2026 — 10:00 AM to 1:00 PM, 2:00 PM to 6:00 PM
Introduction to Archaeology
Discover archaeological excavation.
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Two dig simulators for children and teenagers to explore archaeology and its principles. The activity is led by four archaeologist-educators.
Participation Terms: Free | No reservation required
Schedule: Saturday, September 19, 2026, 2:00 PM ⤏ 6:00 PM | Sunday, September 20, 2026, 10:00 AM ⤏ 1:00 PM, 2:00 PM ⤏ 6:00 PM
Pottery workshop
Want to try your hand at archaeological pottery? Be a potter for the duration of a hands-on workshop. Learn to knead, shape, and smooth by hand using traditional techniques. Create your own piece to take home with you.
Accessible to everyone, even beginners, this workshop is fun, informative, and creative.
Participation requirements: Free | No reservation required
Hours: Saturday, September 19, 2026 ⤏ 2:00 PM to 6:00 PM | Sunday, September 20, 2026 ⤏ 10:00 AM to 1:00 PM, 2:00 PM to 6:00 PM
Reconstruction and demonstration of the ancient potter's wheel
Come explore how ceramics are crafted on a potter's wheel.
Participation guidelines: Free | No reservation required
Hours: Saturday, September 19, 2026, 2:00 PM – 6:00 PM | Sunday, September 20, 2026, 10:00 AM – 1:00 PM, 2:00 PM – 6:00 PM
Numismatic workshop
Dive into the world of money with our numismatic workshop! Explore the history of currency, handle ancient coins, and try your hand at striking your very own coin. A fun, educational experience for ages 8 and up. An interactive session that blends history, creativity, and artisanal craftsmanship.
Participation requirements: Open to ages 8 and up - Free | No reservation required
Hours : Saturday, September 19, 2026, 2:00 PM–6:00 PM | Sunday, September 20, 2026, 10:00 AM–1:00 PM and 2:00 PM–6:00 PM
Guided tour
Discover the Ferme d'Ithe site, a former Cistercian abbey turned modern farm. Built in part on the ancient settlement of Diodurum, glimpses of which you can spot in certain excavation zones!
Participation requirements: Free | No reservation
Schedule: Saturday, September 19, 2026 — 2:00 PM to 6:00 PM | Sunday, September 20, 2026 — 10:00 AM to 1:00 PM, 2:00 PM to 6:00 PM
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Dates and Opening Time
From September 19, 2026 to September 20, 2026
Location
The Ithe Farm
Route de Bazoches
78490 Tremblay sur Mauldre (Le)
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