Via Caracciolo
This is the pedestrian walkway along the Bay of Naples. It's like the Promenade des Anglais in Nice. A nice walk along the water that takes you from the harbour at Mergellina (one of the Hydrofoil piers) to Piazza Vittoria and then to the Castel dell'Ovo (the Castle.) There are street vendors along the way selling food and souveniers. On Sundays, this becomes a pedestrian-only zone. You'll enjoy the view and when you reach the Castle, you can sit down for a nice meal at the many restaurants there.