We have about 24 hours to "kill" between arriving in Civitavecchia and departing from Fiumicino next May. Would you suggest going into Rome for that one night or is there anything of interest (and easier) on the west side of the city? We have visited all the major sites in Rome on past visits and once spent a wonderful day in Ostia. Any thoughts?
Are you staying at a hotel at the airport before flying out or in the city?
We haven't decided yet. If there was something of interest on the west side of the city then we would consider staying in that area.
I'm assuming you're arrival is at the end of a cruise. If so, It will take a while to get off the ship and get to where you are going to stay. And considering the time you need to be at the airport before departure, you probably do not have a full 24 hours -- but I could be wrong. You might want to check out Ostia Antica. Great site with Roman Ruins, and it's close to the airport. There are a number of hotels in the area, so using taxis to get around should not be that expensive or hard to do.
Ostia Antica and also the Portus Romae are a short taxi ride from the airport area.
If you stay in the city then, the options are countless. However even if you decide to stay at the airport because you have an early flight, you can still go to the city by train and be in the city center in half hour.
Since you have already seen Ostia Antica, you might consider Tarquinia, which is a 30 minute bus ride from Civitavecchia. https://tarquiniaturismo.com/?lang=en