Naples was easily my favorite city in Italy, and one of the most interesting. At first glance it's a bit overwhelming - dirty, narrow streets full of crazed mopeds and emphatic Italians, but after a second look it becomes much more charming. Any of the locals are all to happy to give directions to wayward travelers, and even though the streets are confusing it's impossible to stay lost for very long. Lots of historical sites, castles, coastline, pizza stops and markets that are worth a visit.
Insider Tip:Tribunali is fantastic to explore, the coast is beautiful to walk along, and head the hills for a panorama of the city. Pompeii is a quick trip away and definitely worth the venture. Have the pizza, drink the wine, but visit the fish market or any of the markets and find a kitchen.