from the beautiful maestranza bullring , next door to the massive theater , they could see the thirteenth-century torre del oro , the great tower , once clad in gold , part of the fortifications to protect seville from its ancient enemies , the muslims of north africa , the fundamentalist almohads , berbers from morocco who were driven out of seville and all of andalusia in 1230 by the armies of the christian kingdoms of castile and aragon .