Discover this astonishing shell-filled cave for the 2026 Heritage Days.

The Heritage Days are back for the weekend of September 19–20, 2026, in Paris and Île-de-France. It’s a chance to meet the Nymphée Nymphée, a mysterious shell-covered grotto waiting for you in Viry-Châtillon, in the Essonne department. An unusual discovery on the horizon!

There you have it: the Heritage Days are finally back! This weekend of September 19–20, 2026, we’re heading to uncover the finest treasures of Paris and Île-de-France through free tours, quirky activities, and exceptional openings. The museums, monuments, castles and unlisted places will reveal their secrets on this occasion. You got it, it’s the September event not to miss. Especially when the Île-de-France region is your playground. So, ready to explore the program that awaits?

Heritage Days 2026 in Essonne: the must-visit places
Les Journées du Patrimoine 2026 offer a unique chance to uncover the hidden treasures of Essonne (91). From September 19 to 20, 2026, visitors can explore historic sites and quirky locations that open their doors for the occasion. A memorable weekend! [Read more]

Journées du Patrimoine 2026 à Paris: discover the capital’s secret, little-known, and hidden places.
The Journées du Patrimoine return this year with an exceptional edition slated for Saturday, September 19 and Sunday, September 20, 2026. This flagship cultural event offers the chance to visit more than 1,500 sites in Paris and the Île-de-France region, including hidden or little-known spots for the general public... Embark on an adventure, off the beaten track! [Read more]

Heritage Days 2026: Explore Paris and Île-de-France's historic monuments.
Historic monuments of Paris and the Île-de-France region open their doors for this new edition of European Heritage Days. On Saturday, September 19 and Sunday, September 20, 2026, come discover these history-packed gems through a range of charming programs for the whole family. [Read more]

If you're in Essonne, or would like to explore this département to visit its finest treasures, then it's time to show you an unusual spot that awaits you in the town of Viry-Châtillon. Head for the Domaine du Piédefer to discover this rare curiosity. This is the Nymphée Nymphée, a mysterious grotto whose walls are covered with shells and rocks arranged to create a surprising pattern. It's one of the last vestiges of this type of decoration, very popular in Louis XIV's time. It was listed as a Monument Historique on March 22, 1983.

For the Heritage Days 2025, the Nymphée awaits you on the weekend of September 19 and 20, 2026 from 2:30 to 5:30 PM for a free visit. It’s also a chance to set off in search of the Domaine du Piédefer and the lush landscape it offers.

Piedefer Estate

Le programme est mis à jour en fonction des annonces officielles.

Théâtre de Verdure

Le programme est mis à jour en fonction des annonces officielles.

A place of surreal beauty, not to be missed!