Grepolis is a free browser game, MMO of the year in 2012, developed in 2009 by Hamburg-based InnoGames. It is set in ancient Greece and is somewhat similar to the Civilization games in terms of style and gameplay.
A player starts with one city on an island shared with several other players. A variety of buildings can be constructed and upgraded. Various levels of buildings unlock more features. A variety of military units can be recruited. Alliances can be formed. New cities can be created and enemy cities can be looted. Gods and other mythical creatures come into play.
Real money can be used to buy "gold", which has some advantages, though the wiki suggests that they are small.