'Spaccanapoli', the historic centre, is the heart of Naples. Go to Piazza Gusu and pick up a map that shows the locations of the architectural treasures of this area. There are numerous churches, monasteries, palazzos and some great cafés. Whatever you do, don't miss the monastery of Santa Chiara. It's breathtaking. Scarturchio's café has some of the best pastries and coffee in Italy.
Keep your wits about you and you'll be fine.
Piazza Dante underground station. Enter the historic centre through Port'Alba, the city gate behind the statue of Dante.