In 1985, Christo and Jeanne-Claude wrapped the Pont Neuf in gold fabric—430,000 square feet of it—concealing Paris’s oldest bridge for 14 days. Forty years later, the French artist JR has returned to the same bridge with a different proposition: rather than covering it, he has transformed it into a cave. La Caverne du Pont Neuf is a monumental photographic installation visible from the quays, the neighboring bridges, and the Seine itself. —Elena Clavarino