One of the most mesmerizingly macabre (and therefore hugely popular) sights in all Christendom, this otherwise modest museum dedicated to the Capuchin order ends with an eerie series of six chapels in the crypt, adorned with thousands of skulls and bones woven into mosaic “works of art.” To make this allegorical dance of death, the bones of more than 3,700 Capuchin brothers were used. Some of the skeletons are intact, draped with Franciscan habits. The tradition of the friars holds that this was the work of a French Capuchin monk, and literature suggests that you should consider the historical context of its origins: a period when Christians had a rich and creative cult of the dead and great spiritual masters meditated and preached with a skull in hand. Whatever the belief, the experience is undeniably spooky (you can take photographs) so plan wisely if traveling with younger ones. The entrance is halfway up the first staircase on the right of the church of the Convento dei Frati Cappuccini, completed in 1630 and rebuilt in the early 1930s.