I loved the Spanish Steps, at the Piazza de Spagna. I would love to just sit at the steps with someone and "hang out" for a while. But there is always such limited time and I have to hurry to get to the next site.
The Fontana de Trevi is the most famous and arguably the most beautiful fountain in all of Rome. I could spend hours shooting that architecture.
The Trevi Fountain is a little difficult to find on your own. The surrounding streets are crooked and not all of them appear on the map. I am not that great with a map in the first place, and have no sense of direction. But suddenly you turn a corner and there it is.
The figures in the fountain tell a story. The water at the bottom of the fountain represents the sea. Legend has it you will return to Rome if you throw a coin into the water. (I emptied my purse).
Continuing on to Castel Sant'Angelo, the cylindrical building that used to be a fortress, now a museum. Once used as a prison, the Popes turned it into a castle. This castle is connected to St. Peter's Basilica (The Vatican).
I've also visited the Pantheon, the most complete ancient building in Rome. It is absolutely worth it to take the time and go inside. The dome is amazing. Michelangelo studied this dome before beginning his work on St. Peter's Basilica. 
Also steeped in history is the Colosseum. Capable of seating 50,000 spectators, the Colosseum was used for gladiator contests and public spectacles. 
I love every bit of Rome and can not wait to go back sometime and walk the city again. 
