This post covers the Trevi Fountain and Pantheon. The first part covering visiting the Piazza Navona & Chiesa Di Santa Maria Maddalena can be found HERE.
The Trevi Fountain is probably the most famous fountain in Rome so of course, if you are in Rome, you are going to want to visit the site. It's a very short walk from the Pantheon and as you wind your way down narrow streets you will turn the corner and it's suddenly in front of you.
Unlike the Piazza Navona and the Pantheon, there is no courtyard in front of the fountain. It's not a large area so it seems more crowded than most places. I have added a areal view above so you can see how tight the space is.