At last: what looks like a rocky cave covering the Pont Neuf bridge in the heart of Paris (Paris link) is finally open to the public. A disaster was narrowly averted, leaving French artist JR exhausted but happy. Paris has been talking about this unique work of art for months. But four days before the opening, a storm tore through the fabric cladding, causing severe damage. A race against time began, as JR and his team of around 800 worked around the clock to stitch the fabric back together. The "Caverne du Pont Neuf" is now open, nine days behind schedule. The artificial rock grotto is a staggering optical illusion. Creator JR says it's around 15 degrees cooler inside than outside, a welcome relief in the summer heat. The secret behind the elaborate structure almost proved to be its undoing: its chief structural component is air! 80 fabric panels were inflated with 20,000 cubic metres of air to form a gigantic fabric canopy. For Parisians and tourists alike, it's now or never. Pont Neuf can only be experienced like this until the end of June, 24 hours a day and free of charge.