Like horror, here is what you should visit (3).

The Catacombs of Paris :

If we for the catacombs are not particularly scary (if not for reasons annexes as the fact of cross youth gangs with divergent ideals and wanting to put on her face), they remain one of the most places to apeurants foreigners. They are often cited abroad as the most scary place in the world, perhaps because they contrast with the beautiful architecture of Hausmannian Paris, city of love. 

It must be said that the catacombs are full of mass graves and bones: the number of bodies that have been displaced, especially towards the end of the 18th century to cope with the saturation of Paris cemeteries estimated 6 million. 

In addition to this mortuary atmosphere, the ability to access non-public galleries, insecurity, vandalism, etc..