With the backdrop of the Eiffel Tower to one side and Notre Dame to the other, Pont Neuf is not only Paris’s most picturesque bridge but, contrary to what its name suggests, it’s also the city’s oldest.

Yet as of today, Pont Neuf is no longer just a bridge but also an overground cave.

Vast swathes of fabric, woven to look like the stone on which Paris is built, have been inflated over the bridge, creating an art installation called La Caverne. It is a bonkers idea, and a direct tribute to Christo and his wife Jeanne-Claude wrapping the Pont Neuf more than 40 years ago.

The monumental installation is the work of the French artist and photographer known as JR, often called the French Banksy, whose previous installations include making the Louvre pyramid disappear, placing large portraits of Israelis and Palestinians working in the same jobs facing each other along the separation wall and Kikito, a giant picture of a toddler peering over the US-Mexico border fence.

La Caverne finally opened on Monday, 10 days late after the fabric was ripped by sudden gusts of wind requiring emergency repairs. It is billed as an immersive experience, “a crossing”, a “move into the unknown” evoking primeval fears of the dark and being trapped underground unable to escape.

The printed fabric forms a rocky passage with pillars and fissures made to resemble the Lutetian limestone quarried from the underground basins of the Paris region and on which the city, is built. The Pont Neuf, Notre Dame and the Louvre Museum were constructed from the same stone.

The subterranean ambience is heightened by sound – and smell. Thomas Bangalter, one half of Daft Punk, has created an undulating wind-tunnel sound effect; the air has the barely perceptible mustiness of damp soil and rock, created by an expert who makes perfumes in her day job.

JR says he hopes the technically challenging installation, 120m long and 18m high, will lead visitors to forget they are crossing a bridge in the middle of one of the world’s busiest cities.

All of which might have been possible were it not for the shouts of the (mostly American) groups of tourists whose overexcitement could not be contained by fake rock or “subtle soundscape” or the sudden jolt of material reality at the sight of the shop window immediately opposite the exit selling La Caverne souvenirs.

In an interview with the Guardian before the opening, JR, 43, explained his thinking behind the installation which came out of a meeting with Bulgarian-born Christo’s nephew Vladimir Yavachev, who runs the Christo and Jeanne-Claude Foundation.

“We were talking about the anniversary of the Pont Neuf wrapping and Vladimir suggested I do something. Not a wrap but my own thing,” he said. “And then I started dreaming and sketching and as I sketched, the idea of the cave emerged.”

He said the idea of a cave went back to the earliest origins of art when early humans designed on rock walls.

“You’re walking on the bridge. You know exactly where you are, you’re in the middle of Paris. But once you’ve passed the entrance you are somewhere else entirely, not just for a minute but for the whole time because you don’t see the light at the end of the tunnel.

“When we enter the cavern, we won’t see the exit. We’ll have to make a journey through our sources, our origins, to then catch a glimpse of the light. It’s supposed to make you uncomfortable in a certain way.”

Our interview takes place on the Venice Simplon-Orient-Express, the original train of Agatha Christie murder mystery fame. A boy from the Paris banlieue, JR used to tag trains and public transport tunnels with his initials before he found a camera left on a train at Charles de Gaulle airport.

Today, he is journeying the other side of the tracks. Two years ago he was invited to design L’Observatoire, a suite in an early 20th-century Orient Express carriage that he redesigned with the help of more than 100 artisans from across Europe. At an eye-watering £60-£80,000 for the 26-hour journey from Venice to Paris, it is now the world’s most expensive train ticket.

JR appears to have had an open cheque from the train owner Belmond, part of the luxury LVMH group, to create the carriage suite complete with brass bathtub, skylight that opens and closes like a camera aperture and a sitting room with fireplace, but he says L’Observatoire is not about wealth. “It’s art in motion … and something that will last.”

La Caverne, an ephemeral installation and a spectacular feat of engineering, will not. Despite opening 10 days late, it will close as planned on 28 June when the fabric cave will be pulled down and the material recycled.

“It’s like a circus that comes, puts on a spectacle and then it’s gone. But anyone who sees it will remember it every time they pass the Pont Neuf.”