I have been to a couple of Napoli games (admittedly mid-90s) and the atmosphere was unreal, almost anarchic, unlike anything I've ever experienced here.
Its a tatty bowl of a stadium, back then people were getting tickets for the ends and climbing into the dearer sections, no stewards at all and I witnessed one urchin pinching a bloke's season ticket out of his pocket with very long tweezers as they walked past. He saw me looking, smiled and winked, then disappeared.
Crazy city, crazy football. Maradona was truly at home in Naples.