On the outside it's just a gray "concrete monster" that used to be a submarine base, but go inside and you'll enter an immersive digital art exhibit bursting with colors, sounds and glistening reflections on the water.

The "Bassins de Lumières," translated as "Basins of Light," was unveiled by immersive art pioneers, Culturespaces, in an abandoned submarine base in Bordeaux, southwestern France.

The monumental space, consisting of four parallel pools, 110 meters long and 22 meters wide, with a 12-meter-high ceiling, now houses the works of Austrian symbolist painter, Gustav Klimt, as well as Swiss-born German artist Paul Klee.

"When we visited the space, we knew we had to work with it. We had this epiphany and knew we had to put on exhibitions here," Augustin de Cointet de Fillain, director of the Bassins de Lumieres and Culturespaces Digital, told AFP.

"The gigantism did not scare us, the difficulty of the project motivated us: the concrete, the gigantism, the water, the reflections ... It is a magical place," he added.

Visitors to the center, which will open on 10 June, will be able to stroll around the numerous walkways through an immersive experience in which large digitized works of Klimt's art are projected on the concrete walls and reflected on the pools of water.

Klee's exhibit promises to combine painting and music, taking visitors "from an opera overture in an imaginary city to an underwater concerto amidst gold and multicoloured fish, and the rhythm of its geometric structures."

For art and architecture historian Mathieu Marsan, Bordeaux had "turned its back" on the submarine base and its 600,000 cubic meters of reinforced concrete, completed in 1943 by Germany's Nazi occupier, for a long time. After World War II, it was "economically impossible and technically very dangerous" to destroy, Marsan said.

"Basically, we are in the dark, confronted with the works. Whether we are sensitive to art or not, there is bound to be a sensation that will be created," he added.

After a two-month delay due to the coronavirus outbreak, the center will admit visitors, albeit in limited numbers and while wearing face masks.

Culturespaces, which is already piloting the Atelier des lumière in Paris and the Carrières de lumière in Baux-de-Provence, invested 14 million euros ($15.8 million) in the Bordeaux project, which becomes "the largest digital art center in the world."