Viterbo is best reached by bus from Rome. Take Metro line A to the Lepanto stop, then transfer to the Cotral bus to Viterbo — several daily departures, journey time around 2 hours. There is also a regional train from Roma Ostiense via Bracciano (the FL3 line run by Trenitalia), but it is slow and infrequent; the bus is faster and more convenient.
From the north, Viterbo is on the rail line from Orvieto. Daily buses also connect to Civitavecchia on the coast.
Arriving by bus or car, you enter the city through the Porta Romana or the Porta Fiorentina at the northern end. The historic centre is entirely walkable and largely closed to through traffic; park outside the walls and proceed on foot. The Porta Fiorentina is the closest gate to the Rocca Albornoz and the San Francesco basilica.