To travel from San Diego to the Vatican area, you will need to fly to Rome Fiumicino Airport and then take a train or taxi to the Vatican. The cost of a round-trip flight from San Diego to Rome Fiumicino Airport varies depending on the time of year and the airline you choose. Typically, round-trip flights can range from $1,000 to $2,000.
Once you arrive in Rome, you can take a train from Fiumicino Airport to Roma Termini station, which is the main train station in Rome. The train ride takes about 30 minutes and costs around €14. From Roma Termini station, you can take a taxi or bus to the Vatican. A taxi ride takes about 15 minutes and costs around €15-€20.
In total, the cost of a round-trip flight from San Diego to the Vatican area, including transportation from the airport to the city center, can range from $1,500 to $2,500.