Although most of the year is warm (at least in my view), take advantage of the nicer, dryer days to experience Rome from the outside. From parks to squares to outdoor cafes, there's so much to do! My number one recommendation: visit the Orange Gardens, also known as Parco Savello, for great panoramic views of the entire city.
Pretty, fragrant orange trees
I don't recommend eating the fruit itself... A bit tart
Clear skies and bare trees of winter
Whatever you do, don't miss the super interesting Villa del Priorato di Malta, which features the site of a 10th century Benedictine monastery and the famous keyhole of Rome, which grants visitors an intriguing view of the Basilica at Vatican City:
(Not the best quality camera, for the Basilica isn't visible here...)
Another option is always the Colosseum, although you'll need several hours for this if you plan on visiting the Forum and Palatine Hill as well. The latter we didn't reach in time before it closed for New Year's, so I'll be going back this spring.
View of Roman Forum from beside the Colosseum gift shop
Day vs. Night
Next stop: the Pantheon
I suggest reading up on its history; I vaguely remember seeing the name on a PowerPoint back in freshman year but definitely wanted to know more to appreciate the centuries-old architecture.
The dome is really amazing...
