I've been here before, but I've never seen Rome.
Arc of Constantine
The Vatican Museum
St. Peter's Basilica (including the crypt and cupola)
The ancient ruins on Palatine Hill and the Roman Forum
The Pantheon (just finished with restoration)
The Metro (subway) and bus systems
The Trevi Fountain
and the incredible local guides hired by Rick Steves' Tour. They are so good, so knowledgeable, so experienced, philosophical, entertaining, and make it all come so alive and make so much sense and teach us to think for ourselves about the implications of what we are seeing.
Marble everywhere, history alive, so much more... I can't begin to express. The noise, the crowds, the people, the babble, the good food, the unbelievable gelato!
You can see selected photos at this link.