Spain is a fan made expansion available as a free download, and should not to be confused with the later Steam Brothers map.
The map of Spain has some minor rules twists, mainly having to do with the Baleares islands off the coast of Barcelona. These islands have sea routes going to them, start with additional goods, and can have fresh goods put onto them directly by taking the production role. Other than that, the rules are standard AoS.
See Web Links for map and rules in French. For an English translation, see Files.