I was glad we found time to visit the Capuchin Monks Chapel. Its under the Church if the Immaculate on v. veneto. It is 6 crypts decorated with nothing but the human skeleton bones of the monks from the 17th century.
I though it would be a bit like a horror set from a movie but instead I was really moved by just how holy and sacred it felt - I am not at all religious. Its not one for small kids but teens and adults will find it worth a visit.