Similar to RENFE's Rodalies trains, the FGC (Ferrocarrils de Generalitat de la Catalunya) run services to the outskirts of the city centre from their stations underneath the Plaça de Catalunya and the Plaça de Espanya. The excellent website (in English) has plans and schedules. It claims to be the first public transport system in the world to accept Bitcoins.
+34 93 205 15 15
Images by: eldelinux