Looking day-trip suggestions while in Rome

Ostia Antica is always a easy, less than a day trip from Rome. Actually almost a suburb of Rome. An abandon village similar to Pompeii but not the same. Set in a park with lots of trees and shade. Very pleasant and easy to get to via Metro and train. Tivoli and Hadrian's Villa are good, all day, day trips from Rome via bus and/or train. Ron-in-Rome.com has a great detailed, step by step, directions to Tivoli. Also well covered in Steves' Rome guide book. Appian Way, will technically not a day trip, is also a good place to spend Sundays because the traffic is very restricted on Sunday.

There are a number of day trips outside of Rome. There's about as many very interesting tourist sites 10-25 miles out as there are within the center city.
We found Palestrina to be very, very interesting--just outside the town of Zagarolo. It's an ancient pagan temple that had been built over. The Allied bombs of WWII uncovered this massive site--up popped the temple. We were driven to the top of a mountain above Palestrina to a fortress town of Castel San Pietro Romano. We walked down to Palestrina on paths that have been used for 3,000 years.
Zagarolo is also a very unique place where Roman soldiers' helmets were made and where gladiators trained for combat in gymnasiums. The town is on top of a 50' wide ridge with buildings on each side. The basements (underground) are 5-6 stories deep.
In the suburbs, there are also gardens and palaces where the church popes spent their Summers.

Ditto Frank's suggestion about Ostia Antica. Easy to get to and a real change of pace but just as much history.

PS -- BIG advantage to O Antica is no tourists or even locals.

You can also get to Lido di Ostia if you want some beach time.

There are lots of easy options from the historic center of Rome, and you'll find all the details on how to do them in the Rick Steves Rome guidebook. The best value for your time and for ease of travel are Ostia Antica ("Pompeii without the crowds or the dramatic storyline") and Orvieto (hilltop town almost in Tuscany).

Mary Kate, a couple of years ago, I took a Dark Rome day-long bus tour from Rome to the wine country of Tuscany. Lengthy stops at Pienza and Montepulciano, a visit to an abbey at the hour of monks chanting, and lunch at a Brunello di Montalcino winery. Long day, not cheap, but fun, and covered a lot of beautiful territory.

Wow, thank you for all the suggestions. I will get busy researching them. Hard to give up the idea of visiting Pompeii. Our four-day visit to Rome comes at the end of our two week tour of Italy and I thought we may be needing to slow down a bit and smell the roses so to speak.

We just returned from Rome. 5 days in Florence and 7 days in Rome. We visited Ostia Antica instead of Pompeii. It was a great choice. The ruins are virtually deserted. Very peaceful and quiet. Lots of trees for shade. To top it off we were able to speak with archeologists working at a site close to the entrance. They said that Pompeii is too crowded and is a tourist trap. It took half a day. Value is 5 stars!
George

I used Rick's audio guide for Ostia Antica. Good tour, excellent sight. Tivoli and Hadrian's Villa are still on my list, just hasn't worked out yet. Next time . . .