We will be taking Rick's "Southern Italy Tour" next late April 2018. We will be arriving 3 days before the tour starts in Rome and wanted to visit some cities/towns within a train ride or car ride from Rome. We have been to Florence and Assisi already.
Appreciate any suggestions !!
Orvieto is one
If you're interested in ancient ruins, you could visit Ostia Antica.
Tivoli, for the magnificent Villa d'Este gardens.
Looks like the tour stops in Tivoli but doesn't go to Villa d'Este - or even spend much (any?) time in Tivoli, only a visit to Hadrian's Villa.
Sperlonga.
Another vote for a day trip to Ostia Antica. It's very close by, easy and cheap to get there on public transit, not crowded at all, and really terrific ruins.