I believe that Spain must have the most useless unique "bonuses" as a civilization. Its unique building, Citadel, is completely useless. Bar none It doesn't have any effect vs gunpowder units and at this time, gunpowder is right around the corner! The whole concept of castles was poorly implemented and probably should have been done earlier in the game or given different bonuses. Unique Unit - Conquistador is also pretty weak and only nominally improved over the Cuirasser. Unique Power - Naval units have 2 extra moves...OK I get the point of it, but compared with the UP of other civs it's again, pretty weak. All in all, it is kind of sad that a civilization with as interesting a history has Spain has such boring/useless unique powers.