In Episode 3 of the anime series, the Searchers come across the ruins of an English-looking fortress, complete with courtyard and stone archways. The courtyard is full of lost discs, and they find a Golem guarding the place. He was sworn as its protector by the king from not too long ago, after a battle took place there against Moo's forces.
It is probable that the battle that Holly tells Genki about in Episode 1 of the series (in which a human king tried to fight back against Moo's takeover) took place at this fortress. It is unknown who the king was, since he obviously didn't survive.