Capua was once one of the most important cities in the Roman Empire. The Via Appia was built to link Rome with Capua. Capua also has the empire's second largest amphitheater, after the Colosseum, and likely the first stone amphitheater built in Italy.
What's more, visitors can enter the subterranean passageways where animals, gladiators, weapons, props and scenery were kept, as well as view the elevator shafts that brought them (and Spartacus) to the arena. There's a Gladiator Museum and good restaurant on the premesis.
This site doesn't draw large crowds; we were the only ones on the grounds. It's clean, fairly well-maintained, and a must-see, half-day excursion for anyone in the area.
Cost: 5 Euros for admission (2.50 per adult), parking is free, and 20 Euros for lunch
Travel time: Capua is roughly 12 km from Naples Support Site
Time on site: 2 hours