The old walled city is compact and best explored on foot — the circular Venetian walls enclose an area about 1 km across, and all the main sights are within easy walking distance of each other. Most visitors to the old town can cover everything they want without needing any transport at all.
Beyond the old city, Nicosia is a sprawling modern capital best navigated by car or taxi. The urban bus network (OSEL in the south) is functional but routes are designed for commuters rather than sightseers. Taxis are metered, plentiful, and by European standards affordable — a ride across the city rarely costs more than €10–15. Ride-hailing apps also operate.
Note that crossing into North Nicosia requires passing through the Ledra Street checkpoint on foot — you cannot drive through. Once on the northern side, minibuses and shared taxis are the main local options.