In 1474, a twenty-three year old woman ascended the throne of Castile, the largest and strongest kingdom in Spain. Ahead of her lay the considerable challenge not only of being a young, female ruler in an overwhelmingly male-dominated world, but also of reforming a major European kingdom that was riddled with crime, corruption, and violent political factionism. Her marriage to Ferdinand of Aragon was crucial to her success, bringing together as it did two kingdoms, but it was a royal partnership in which Isabella more than held her own.