I'm planning a trip to Florence & Cinque Terre in early May with my girlfriend. Originally I was planning on a day trip to Siena from Florence, but after seeing some of the quicker than I remember train times to Rome (is 1.5 hours really accurate), I'm now questioning going to Rome for a day, then back to Florence that night instead.
I studied in Rome 8 or 9 years ago, so it would be nice to reminisce; my girlfriend has never been to Italy. I have a fairly good idea of how to get to the sites around Rome and understand that 1 day is far from enough time to fully explore Rome. Most museums would be out, but it would be nice to see the Colosseum, Piazza Navona, Trevi Fountain, Vatican, Sistine Chapel if the line permits, etc.
Does anyone know how much a round-trip ticket would be on one of the quicker trains?
Would we be missing out by not seeing Siena (I've never been)?
Thanks.