Agrigento has some Greek ruins, think something very similar to the Acropolis,
In the very centre Piazza Armerina has a neat archeological area, I believe it was the where the people lived who sourced all the animals for the Colosseum in the Roman Era. The entire palace is covered in tile mosaics depicting life at the time. They were restoring it while we were there 4 years ago, neat place.
Mt. Etna - already discussed
Taormina, Province of Messina, Sicilia, Italy This is a neat town nestled on a hill top. Really cool place that once you have finished weaving your way through town, you end up in a Greek amphitheater that over looks the Ionian Sea. I would highly recommend this place.