300: Rise of an Empire (originally titled Xerxes, and then titled Battle of Artemisia) covers the story of another battle which occurred simultaneously with the one depicted in the first film - which had a great impact on the events we are already familiar with.
The Starz historical action serial, Spartacus, based on the story of the leader of a roman slave rebellion, will be coming to an end soon, but the network claims the final season is going to be well worth it.