of the big cities in Italy, Naples is probably one of the least impressive. Not that there aren't cool things to do/see there, but if you have a limited time in Italy, I'd try to spend my time elsewhere. However, if you're in the area, Pompeii is a must. There's a train the runs around Mt. Vesuvius, connecting Naples and Pompeii, called the Circumvesuviano - it makes life a bit easier. Exchange Amalfi for Capri. To get there, take the Circumvesuviano to Sorrento, and then the bus to Amalfi. The bus ride offered the most impressive sites I've ever seen, and I didn't have to worry about driving with those insane Italian drivers.
As said before, Rome and Florence shouldn't be passed up. I haven't heard great things about Milan, but if you're in the northwest portion of Italy, definitely drive along and visit the towns of Cinque Terre.
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