Why... does that exist anywhere?
To say this is a museum full of mummies doesn't even come close to conveying the unspeakable horror of this place. How about this: In ancient Rome, and college fraternities, there is a brutal and humiliating tradition known as running the gauntlet, during which you strip naked and run through a valley of horrors. Guanajuato's El Museo De Las Momias ("Museum of the Mummies") is just like that, except that it's the spectators who are naked. And dead.
You know one of those hands will reach out and grab you.
The Mummies of Guanajuato are naturally preserved bodies from a cholera outbreak that hit Guanajuato way back in 1833. Since this is basically just a huge open grave with floodlights, its legality and moral status continues to be the subject of much discussion everywhere except in Mexico.