Rome to Barcelona

The basic trip will take over 23 hours and require at least 4 transfers even if you do not deviate from the most direct route. That would be an awful lot of time spent sitting on trains--and I do love trains.

Not all routings between Rome and Barcelona take the same path. I liked Milan and Lyon and am very much looking forward to seeing Turin on my next trip to northern Italy. Some departures include the regional train line along the Riviera, with stops in places like Nice and Antibes--both good destinations. Genoa and Marseille are also possible--both interesting but grittier cities. There are options in Provence (Aix-en-Provence, Nimes, etc.) and then good possibilities along the French coast, including Montpellier. After you cross the border into Spain, there's a stop in historic Girona.

There must be about 100 potential stops along the way if you consider all the different routes possible.

I would go from Rome Termini to Fiumicino. Then from Fiumicino to El Prat. Finally from El Prat to Barcelona Saints. Two stops.

If you have a week to do this you can certainly make this an interesting trip.

There are direct trains to Barcelona form Lyon and Marseilles, and those also stop in places like Nimes and Montpelier.

So from Rome you could go up along the coast and spend a few nights on the Ligurian Coast. Genoa as mentioned is an interesting city too. Then the next stop could be somewhere on the French Riviera.

in theory you could even to this all on regional trains, just following the coast from Rome to Barcelona, stopping over in any place along the route that catches your fancy.

The Deutsche Bahn website is telling me an all-regional-train routing would take over 31 hours and require 9 transfers.

I went by train from Genoa to Barcelona several years ago. Instead of being a romantic black-and-white movie from the 1940's, it was more like torture. Not much interesting scenery, endless mystery stops, poor eating choices, totally disturbed sleep. A better use of your time is to fly and then take side trips for variety.

I'd fly to Barcelona and then use it as a base for some day tripping in the area.