A couple of September classics:
- Sept 10th: Fête du Port, a popular evening with food, drink, music and dance at the Port, from 7pm
- Sept 17th and 18th: Journées européennes du Patrimoine, free access to all the monuments in town, even late at night - possible to visit various sights not usually accessible to the public

And also:
- from Sept 12th to 28th Cirque Gruss, circus at the Esplanade Lattre de Tassigny, behind the Acropolis congress centre
- Sept 22nd: George Michael "Symphonica" at the Palais Nikaia