On foot
Walking is by far the best way to see the historic centre. The centro storico is compact — the Pantheon, Piazza Navona, Campo de' Fiori, and the river are all within 15 minutes of each other on foot. The Vatican is a 30-minute walk from the centre or a short metro ride. Comfortable shoes matter; the cobblestones are relentless.
By metro
Rome has three metro lines operated by ATAC. Lines A (orange) and B (blue) intersect at Termini. Line C (green), which opened in phases from 2014, runs from Monte Compatri-Pantano in the southeast to San Giovanni (where it connects with Line A) — its extension to the centre is ongoing. The metro is fast but limited: most of the historic centre has no stations, largely because construction keeps hitting ancient ruins. The metro runs roughly 05:30–23:30 (until 01:30 on Fridays and Saturdays).
By bus and tram
ATAC buses cover the city extensively and reach areas the metro doesn't. The most useful tourist routes run along the main boulevards (buses 40, 64 connect Termini with the Vatican). Tram 8 is handy for Trastevere. Frequency is inconsistent; use the ATAC app or Google Maps for live times.
Tickets
A single BIT ticket costs €1.50 and is valid for 100 minutes on all buses, trams, and metro (one metro journey only). Multi-day passes: 24h €7, 48h €12.50, 72h €18, 7-day €24. Buy tickets at tabacchi (tobacconists), newsstands, metro station machines, or the ATAC app. Validate every ticket when boarding — inspectors do check, and the on-the-spot fine is €54.
By taxi
Taxis are metered and relatively honest. Fixed fares apply to/from both airports. Hail on the street, find a rank (outside Termini, at major piazzas), or use the itTaxi or FREE NOW apps. Ride-hailing apps like Uber operate only with licensed drivers here and are not cheaper than taxis.
By scooter or e-bike
Electric scooters (Lime, Bird, Tier) and e-bikes are widely available via app and are useful for covering longer distances along the river or to Testaccio and Pigneto. Riding a scooter in Rome traffic is not for the faint-hearted; the roads and the drivers are both unpredictable.
Driving
Don't. Parking is nearly impossible in the centre, the ZTL camera system issues automatic fines to foreign plates, and the traffic is genuinely chaotic. Leave the car at a park-and-ride on the ring road and take public transport in.