Ostia Antica

Kent is correct -- need to know where and when you intend to drop car and where are you coming from. OA and the airport are on the same side of Rome so it would make sense to visit OA and then drop the car at the airport and take LExpress into Rome -- if coming into Rome from that direction. There is a huge parking lot at OA and the demand is fairly low so parking would not be a problem. If on the other hand you are in Rome then it would make more sense to drop the car and use the metro/train for OA.

In b) you didn't say where you would get rid of the car, it makes a difference in how the question is answered.

Option C. Get rid of the car, go to the hotel in Rome and take the metro to OA. You have to change lines, but that's free of charge. So it costs only one ticket each way.

We did essentially what you describe. We leased a car in Amsterdam drove through Germany, Austria and Northern Italy. When we arrived in Rome, we drove to Ostia Antica then dropped the car off at the ariport (I don't recall which airport) and took the train into town to our lodging.

It worked out well except we lost most of an hour trying to locate the person to accept our car. We found the office without a problem, we had made an appointment and called ahead to confirm but still the office was abandoned when we arrived. It took awhile to reach the guy and longer to actually find him. I suspect it was just that we were in Italy where few can be bothered with punctuality. He probably let the appointment slip his mind while he enjoyed a long lunch (or went home really early and had to come back).

We've done that twice. We stayed at the Holiday Inn, Parco Demedici (sp) expensive but worth it. Great breakfast, losey dinner. We took a cab to OA but the holiday inn shuttle bus to the city and the airport. We had an Avis car which Avis picked up at the Hotel, on the first day. Not much parking at OA and a lot of worthwhile walking. Good little Tattoria (sp) on premises.
Have a great trip, Joe