European Heritage Days in Boulogne-Billancourt: the city in images

More confidential, and probably the most moving appointment of the weekend: the studio of Frank Horvat, the fashion photographer who worked in Boulogne, opens on Saturday 19 September. Half a century of prints and archives is presented there by the artist's daughter herself. Places are few, so plan your registration early.

At the municipal archives, finally, the archivists take visitors into their conservation rooms on Saturday at 10am, booking required. The next day, the reading room turns into an escape game, "Panique aux Archives!", played in teams of four to six. An unexpected way to draw children into the story of the town and the treasures it protects.

Île Seguin, La Seine Musicale and the Renault legacy

Walk down towards the Seine and the setting changes completely. Where the Renault factories once ran, the île Seguin has become an open départemental park and an open-air museum.

At the Pavillon des projets, the "Voyage en Industries" route can be followed with the memory keepers of the AMETIS and ATRIS associations, former employees of the site, or with Emmanuelle Dupuy, who worked at Renault-Billancourt and co-founded its women's group. Their accounts give the industrial story a depth no information panel can match. The route passes La Folie de l'île Seguin, a sculpture by Chloé Quenum made from spare parts of Renault models and set near the pont Daydé, at the old factory entrance. On Sunday afternoon, a family workshop for children aged 6 to 11, "Mémoire en folie", extends the experience. These activities are free and require booking.

On Saturday only, La Seine Musicale holds its open day from 10am to 6pm. The vessel designed by Shigeru Ban and Jean de Gastines can be explored on a guided tour, alongside indoor and outdoor concerts, open rehearsals, the SeineLab workshops for young audiences run with the mediators of the Ircam-Centre Pompidou, virtual reality experiences and a Club space for families. It is the most complete event of the weekend, and it is not repeated on Sunday, so note it first.

The espace Landowski hosts two moments of classical music carried by young performers: on Saturday at 3pm, pupils of the Prizma school, aged 10 to 18, play Bach, Mozart and Chopin on piano, violin and cello; on Sunday at 5pm, the duo formed by Mathilde Reuzé on violin and Gabriel Rostagni on cello, both trained at the Académie musicale Philippe Jaroussky and now artists in residence at La Seine Musicale, offers a chamber programme in the musée des Années 30, among its Art Deco exhibition rooms. At the Musée Paul Belmondo, a wind quintet from the conservatoire takes over in the late afternoon.

Special mention for the concert by the chamber choir Les Divertissements, on Sunday at 3.30pm at the église protestante unie: it opens with a prayer written by Francis Poulenc on the eve of the Second World War and closes with Schubert, moving from anxiety to peace. Entry is free, with voluntary participation towards costs.

Unusual openings: the doors that open once a year

A few places are truly accessible only this weekend. The maison Marie-Walewska, rented by Napoleon I in 1811 and 1812 for the young Polish countess, can be seen on Sunday on guided tours, booking required with the tourist office. Listed on the national inventory since 1986, emptied of its furniture but intact from the street, it was forgotten for a long time.

The town hall, at 26 avenue André-Morizet, also opens on Sunday, with no ticket or booking. Built in 1934 by the architect Tony Garnier with senator-mayor André Morizet, this grand civic building sealed the union of Boulogne and Billancourt and remains a major piece of 20th century French architectural heritage.

For the fiftieth anniversary of the Loto, the draw studios based in the city open to the public for the very first time, on both days. The embassy of Mongolia welcomes visitors on Saturday. Add to your plan the 1930s architectural route, following Le Corbusier, Mallet-Stevens and Lurçat, along with the résidence du Point-du-Jour, a major ensemble designed by Fernand Pouillon between 1957 and 1963.