Construction of the Roma-Lido line began shortly after the end of the first world war and was completed some six years later in 1924. It began operation as a steam locomotion railway but electrification was completed less than a year later.

The line currently is operated an integrated part of the metro system, but is entirely overland. It runs from the Roma Porta San Paolo station beside the Pyramide metro B line station and runs alongside the B line as far as EUR Magliana. It then continues separately on to the seaside town of Ostia. The line terminates beside the end of Via Cristoforo Colombo