This is my 3rd visit and I have gone to several of these hidden gems. I actually accidently walked right past the Pyramid of Cestius without having any idea what it was.
I plan to spend a little more time in Villa Borghese, and I love the churches. I have made a decision to skip the Trevi Fountain because it has become just about impossible.
There were earlier Etruscan pyramids in other towns in Italy, but I think they're only known from surviving descriptions in Roman sources. Apparently all of them were demolished, probably for building materials. Cestius wound up incorporated into the Aurelian Wall if memory serves.