The centro storico of Rome comprises that which stood inside the 3rd-century walls of the city; it contains most of the major tourist sights. The borders are roughly the Vatican to the east, Villa Borghese to the north, Termini station to west, and the Colosseum to the south. This large area is easier to navigate when divided into smaller modern neighborhoods.
Fortunately for tourists, many of Rome's main attractions are concentrated in the centro storico and can be covered on foot. In addition, Rome has a good network of public transport, both above and below ground. The Metro Linea A will take you to Termini station, the Trevi Fountain (Barberini stop), the Spanish Steps (Spagna stop), St. Peter’s (Ottaviano), and the Vatican Museums (Cipro), to name a few.
Single tickets (BIT) for the bus and Metro cost €1.50 and must be purchased before boarding. They are available at Termini station, from automatic ticket machines in Metro stations, and at most newsstands. These tickets can be used on all city buses and trams for 100 minutes or for a single Metro ride. A day pass (Roma 24h) covering all public transport costs €7, while a weekly ticket (CIS) is €24. Children under 10 travel free on all public transport when accompanied by an adult.