A monks' cemetery in the basement of a church that is entirely decorated with the bones and skulls of over 4,000 Capuchin monks who died between 1528 and 1870. Entrance is to the right of the staircase at Church of the Immaculate Conception (Santa Maria della Concezione dei Cappuccini); free, but donations are accepted. It is the spookiest thing I have ever seen (one of four such chapels in Europe) mostly because of the monks' skeletons dressed in robes..don't go there with your small children unless they like bones..
Address:
27, Via Veneto near Piazza Barberini Rome Lazio Italy