From Leonardo da Vinci Airport (Fiumicino): Rail link every 15 minutes on the FM1 Roma/Fara Sabina/Orte line - do not take the non-stop Leonardo Express train to Roma Termini - get off after around 20 minutes at Roma Trastevere, on the same platform then take the train on the FM3 line to Viterbo or Bracciano (around 50 min) - do not take the train to Cesano. Departures during the day: every 30 minutes.
From Ciampino Airport : Regional Bus Lines, Cotral to the underground line A, Anagnina station. Take the underground to the Valle Aurelia underground/rail exchange then take the train on the FM3 line to Viterbo or Bracciano (around 50 min) - do not take the train to Cesano. Departures during the day: every 30 minutes.