Nice Côte d’Azur Airport: Take Tram 2 to Jean Médecin for central Nice (about 25–30 minutes). Do not automatically buy the €10 airport fare: ride free to Grand Arénas, get off, buy a standard contactless Lignes d’Azur ticket (about €1.70; validity/fare rules can change), then continue from the same stop. For Vieux Nice, Bus 12 along the Promenade is slower but direct. Uber/Bolt to the centre is roughly €20; ordinary taxis are poor value.
Nice-Ville railway station: This is the useful central station for Paris TGVs, the night train and Riviera TERs. Jean Médecin is a short walk away; Vieux Nice and the Promenade are roughly 15–20 minutes on foot, or use Tram 1. Do not confuse it with Nice-Saint-Augustin (best for the airport) or Nice-Riquier.
Nice-Saint-Augustin / Grand Arénas: Use this station if arriving from or continuing along the coast and you need the airport: it is beside Grand Arénas, linked free by Tram 2 between the station and both airport terminals. TER trains serve Nice-Ville, Monaco/Menton and Cannes/Antibes; it is not a substitute for Nice-Ville if you want to start sightseeing on foot.