It is a cemetery and a consecrated spot located in the abandoned limestone quarries under the streets of Paris. (They started removing bones from overcrowded cemeteries all over Paris in 1786 and stopped in 1860. Some five to six million skeletons were moved.) However, it's really creepy and probably one that you could cross off your list unless you've been in Paris forever and have seen EVERYTHING else, or you like creepy.
OK, Eric, don't shoot me.
The other creepy thing I paid good euros to see was a temporary exhibition of George Condo's "work" (which can better be described as hideous) even though he is apparently greatly appreciated by many (?). Poor Aristide Maillol, whose lovely work fills the Musee Maillol, must be spinning in his grave.
Hurry, you only have until August 17 to see George Condo's "work" at Musee Maillol, 61 rue de Grenelle 75007!
Lucky Andy Warhol...