• The Cathedral of Notre Dame, the 12th-century Gothic church built on the Ile de la Cité in the middle of the river Seine, visited by more than 14 million people each year, is in trouble.

    After surviving the French Revolution and two world wars, Notre Dame faces the biggest threat to its existence yet: it’s falling apart. According to Time, centuries of weather and pollution and some shoddy 19th-century restoration work have left the cathedral crumbling and in desperate need of repair.

    “Pollution is the biggest culprit,” Philippe Villeneuve, architect in chief of historic monuments in France, told Time. “We need to replace the ruined stones. We need to replace the joints with traditional materials. This is going to be extensive.”

    When it became clear that Notre Dame would need extensive repairs the French government was not prepared to finance, the Archbishop of Paris and the Diocese of Paris created the Friends of Notre-Dame de Paris to raise the $100 million needed to save the cathedral.

    Among the issues plaguing Notre Dame are the crumbling pinnacles, gargoyles, stained glass work, and — of most concern to the foundation overseeing the restoration — the flying buttresses.

    According to the Friends’ website, “The poor state of the stonework is particularly problematic with respect to the flying buttresses. Should even one of these structural pylons fail because of the damaged stonework, the consequences would be disastrous.”

    Take a 360-degree tour to see what needs to be done to save Notre Dame:

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