But like plenty of other postindustrial sites—the power station in London that’s now the Tate Modern and the distillery in Milan was reborn as the Prada Foundation—culture has flowed like water into the spaces that industry left behind. In this case, a radical new arts campus is rising from the ashes of the rail yard, in the private hands of Maja Hoffmann, a Swiss pharma­ceutical heiress, philanthropist, and collector of contemporary art who arrived in Arles at just a few weeks old and considers it her hometown. Her foundation, Luma, begun in 2004 with the mission of spurring artistic activity rather than just exhibiting its results, will spend a sum estimated to be north of $100 million on the project. The centerpiece of the new Parc des Ateliers site is Frank Gehry’s dazzling (literally, with its stainless-steel cladding) 185-foot-high tower for an art and research center, which will open in 2018. Its architect says the clustered blocks were inspired by the rock formations that occur naturally in the region.

In the meantime, New York–based Selldorf Architects completed the stunning conversion of two nearby buildings last summer: Les Forges, or the foundry building, and the Mécanique Générale, which had been the main repair space. The adapted structures have already hosted a range of events, including performances by Benjamin Millepied’s L.A. Dance Project and an installation by artist Jordan Wolfson of a puppet in chains being thrown violently to the floor.

The firm’s principal, Annabelle Selldorf, was charged with not only turning the buildings into galleries but also creating a master plan for the Parc. She was a natural choice, having both a long-standing relationship with the art world and a reputation for subtle renovation projects, such as making over a Manhattan roller-skating rink as an art gallery for Hauser + Wirth in 2013. “My work is about pro­portions, light, and integrity of structure: what the building brings to the project,” the architect says.

When Selldorf first visited Arles, she says, she “couldn’t take in the incredible size of the site.” The cavernous space is 23 feet below the street, on the same level as the railway. “You descend a slope to enter it. And this is not a park in the usual sense—there’s all that dusty gravel and intense sun,” she adds. Accordingly, Selldorf is working with the Belgian landscape designer Bas Smets on developing a softer context, with newly introduced undulations and greenery that will guide visitors from building to building and create what Hoffmann calls “a public garden for my fellow citizens.”

At Les Forges, the architect inherited a gabled structure of soaring columns, steel trusses, and limestone walls. In this former foundry, Selldorf replaced the old roof and its terracotta tiles, stabilized the cast-iron framework, installed concrete floors, and added a mezzanine level to create a total of 31,000 square feet of gallery space. To bring light to the interior, she inserted glazing in the upper and some of the lower windows, where smaller panes or plywood had been placed; she also added a few skylights. In the middle of Les Forges is an alfresco courtyard café, another amenity in this dramatic, elongated volume. “The galleries have worked really well for conferences and symposia through the winter, too,” notes Selldorf.

The Mécanique building now offers a heroic, open-plan exhibition space of 48,000 square feet, mostly on one floor. Here the cast-iron structure with stuccoed limestone walls needed less extensive repairs. But Selldorf has added a 65-foot-long, column-free extension along the west elevation that mimics the structure’s gabled bays—but with a dark gray concrete-block facade and zinc roof whose new materials allude to the building’s past: A section had burned down years ago, and the remaining part was simply sealed with concrete blocks. Selldorf has rewritten this history using contemporary architectural language.

The vastness and flexibility of the hall allows a multitude of uses. Last summer, the space accommodated a huge photography show with the insertion of diagonal walls while in an area behind that, dancers performed for an audience seated on temporary bleachers. Washed by day with natural light entering through new elongated glass strips, the revitalized Mécanique felt surprisingly intimate at night.

The site’s other major building—a 54,000-square-foot old boiler house called La Grande Halle—was reconfigured in 2008 as a multi­purpose structure. French architects Alain Moatti and Henri Rivière added a steel-mesh wall to the west side and a supersize LED screen on the north.

Several more renovations are in the works. Another redo by Selldorf, La Formation, is being made into a dance studio and an artists’ residence. A cluster of structures at one corner of the site, on part of the ground floor, has an orientation center, but more is planned there, including a hotel. All in all, the blossoming Parc des Ateliers is already creating its own history: the transition from industry to art that tells a truly 21st-century story.