Age of Empires II: Age of Kings (1999) is a historically based real time strategy game developed by Ensemble Studios and published by Microsoft Games. While it's predecessor, Age of Empires, was set in Ancient times, AoE2 is set in the Middle Ages and covers a wide selection of cultures - thirteen in all. These civilizations share four sets of graphic styles, and their character is revealed by the way they play on the field. AoE2 has a decidedly outdoor feel and a nice sense of "realism". AoE2's expansion, The Conquerors adds four new civilizations and some extra historical characters (Attila the Hun and the Aztecs spring to mind), but unfortunately I just haven't had time to get around and look at it. Many of the major AoE2 fan sites will help you out there.