2-3 hour taxi tour of Rome?

You realize you will need to go through Immigration to leave the airport? The queues at FCO can be quite horrendous depending on time of day. I recall it took me a good hour and a half to get from plane to Immigration and through even using my British passport when Britain was part of the EU. Again depending on time of arrival and traffic into Rome it could be an hour to make the trip into Rome. It always sounds so easy to do but may not be. Too many things can go wrong - plane late, strike, accident, etc.

You don't have five hours. That is sort of the sucker play. It will take an hour from landing to being in front of the airport looking for a cab and another 30, 45 to make it downtown Rome. Traffic is pretty slow in the city but you would have about another hour for the taxi to drive around -- Now you have used about three hours and need to head back to the airport. Later afternoon traffic can be slow so allow an hour for return. Back at the airport with about an hour to an hour and a half to go through security. Now if you hit any type of delay, it could be getting tight. Goood Luck.

I hate to pile on, but the PPs are right. 5 hours isn't enough time to comfortably and safely do what you want to do. Even though, on a flight from Athens to Croatia you wouldn't have Immigration on either arrival or departure. You still have to deal with security on return go the airport, and being FCO, I'd want to be there 2 hrs before departure.

hey hey sassy
wow, agreeing with others. i would not count on this even if i could part the red sea.
@CJean gonna pile it on also, many don't wanna hear it :)
is the 5 hours total from arriving in rome to departing for split. rome is at least an hour away from airport. going through customs/passports, where you putting your bags, it's jubilee 2025 with millions of people everywhere, asking a driver to "hurry" through crowded streets with some closed and blocked, then a ride back to airport to check in again. if miss flight, you will need a new ticket.
i would have spent 2 nights in rome before going to split to show your grandson, i wouldn't get him excited about seeing rome then it doesn't happen. what does not "high-end pricey tour" mean in euros? good luck and enjoy
aloha

Thanks for all your thoughtful (and sensible) replies. We'll keep it simple and enjoy the Fumicino scene!
S