This church and convent complex safeguards what is possibly Rome's strangest sight: crypt chapels where everything from the picture frames to the light fittings is made of human bones. Between 1732 and 1775 resident Capuchin monks used the bones of 3700 of their departed brothers to create this macabre memento mori (reminder of death) – a 30m-long passageway ensnaring six crypts, each named after the type of bone used to decorate (skulls, shin bones, pelvises etc).
There’s an arch crafted from hundreds of skulls, vertebrae used as fleurs-de-lis, and light fixtures made of femurs. The accompanying multimedia museum tells the story of the Capuchin order of monks, including a work attributed to Caravaggio: St Francis in Meditation. Don't miss the adjoining Chiesa dei Cappuccini (1626), accessible via the outside staircase.