Final answer:
The marriage between King Ferdinand of Aragon and Queen Isabella of Castile led to the unification of Spain and marked the beginning of Spain's age of global exploration and colonization.
Step-by-step explanation:
The royal marriage between King Ferdinand of Aragon and Queen Isabella of Castile in 1469 united the two kingdoms to form Spain. This pivotal event in European history marked the foundation of modern Spain. Their union also played a critical role in the Spanish Reconquista, ending the rule of the Moors with the conquest of Granada in 1492, and establishing Spain as a significant power ready to embark on vast global explorations and establish a vast empire during the Age of Discovery.