French artist JR, popular for his large-scale projects from photographs to graffiti and street art, wants Parisians to do something unusual: stop for an immersive experience on the city’s oldest bridge, Pont Neuf. In June, he plans to transform the bustling bridge that dates back to the 17th century into a walk-through “cave” — a temporary, monumental public artwork that will cover the stone arches with a rocky illusion and invite visitors to cross the River Seine through a tunnel complete with sound and digitally augmented reality. He says his project may be the “largest immersive installation ever made.”