Possible Clues:

• Greek city painting in watering place
• Ancient rival of Athens
• A state of discipline at a convenience store ... thanks!
• Old Athenian ally against Persia
• What the 300 defended
• Aggressive ancient city-state
• Filmdom's ''In the Heat of the Night'' city
• Old city region held by weaponless army
• Dominant city of Greece, once
• Part of Greece once storing pictures in resort