PARIS, France: Paris's oldest bridge appeared to be swallowed by a mountain on May 21 as street artist JR, often called the "French Banksy," unveiled a striking installation that wraps the Pont Neuf in a giant inflatable "cave."

It transformed the 17th-century crossing over the Seine into a dramatic rocky illusion.

JR says his project, La Caverne du Pont Neuf, is meant to bring nature and stone back into the center of Paris. He explains that he is not really hiding the bridge but showing the kind of limestone once quarried to build the city itself.

Now, the bridge looks as if it is covered by rough gray rocks rising above its arches. From a distance, it almost disappears beneath what appears to be a giant cliff, with openings resembling dark cave entrances above the water.

The structure was inflated overnight after weather delays and is the most important stage of a project that has taken more than a year. JR described it as a huge puzzle finally coming together, with air filling the structure so the "rocks" rise nearly 18 meters high and stay in place.

This is one of the biggest public artworks in Paris in many years, funded by the sale of JR's art and support from some companies. It will open to the public on June 6.

Since March, the transformation has been recorded with time-lapse cameras, showing the bridge slowly disappearing.

Early on the morning of May 21, JR and his team began inflating the giant cave over the bridge. From the outside, it looks like a rocky formation breaking into the city landscape. JR, known for placing large photos on buildings around the world, is often compared to Banksy.

People passing by reacted differently. Julien Moreau, 34, said that usually people walk across the bridge without noticing it, but that morning everyone stopped to look, which he felt was part of the artwork.

JR said he wanted people to pause on the bridge rather than rush. He admitted the team felt nervous, but said that working in public and taking risks is part of the beauty of such a project. Some people, he said, might not notice it at all, while others will be amazed.

The structure is about 120 meters long and 18 meters tall, as high as a six-story building. Even so, it is mostly air, with 80 fabric sections filled with about 20,000 cubic meters of air, and it weighs only around five tons.

Engineers tested the design for weeks to ensure it would remain stable even if the air supply were cut. The fabric was carefully stitched by 25 workers in Brittany.

Visitors will be able to walk through a long, dark tunnel inside it for free, entering darkness and then coming out into the light. JR says each person can experience it in their own way and imagine their own meaning.

The artwork also honors a famous Parisian artist from the past.