One of the Capuchin monks got creative back in the day and decorated a series of chapels with the remains of his fellow monks. Each element of the decor is done with the same body part, some entirely of hip bones, others of ribs, jawbones, etc.
There are even a few entire bodies thrown in, dressed in robes, some standing around keeping an eye on things.
Rome has been toasty hot so the Trevi Fountain was a great way to cool down. The shady interior of the Parthenon felt mighty good too.