Some of these sites result from a phenomenon that has naturally (or supernaturally?) mummified the dead, while others consist of artful arrangements of bones and skulls done by a creative monk in his spare time. In addition to such collections of human remains, many saints whose bodies have been miraculously preserved are on display in churches. (There's also a Buddhist example of the miracle in Siberia.)

Such displays of the dead certainly appeal to travelers with a taste towards the macabre, but they can also provide reflective travelers with a powerful reminder of the impermanence of life. Whatever your reason for checking out the dead on display, the sites below are widely recognized as among the best in the world. Also listed are individual preserved bodies of saints and other famous figures.
More info here: http://ngm.nationalgeographic.com/2009/02/sicily-crypts/gill-text