Christopher Columbus was a navigator and explorer of Genoese origin, primarily active in the service of the Spanish Crown. His career is defined by the four transatlantic voyages he undertook between 1492 and 1504, aiming to find a western sea route to the Indies. Columbus's main achievement was establishing lasting contact between the Eastern and Western Hemispheres, initiating the era of European exploration of the Americas and the process known as the Columbian Exchange. During his expeditions, he explored numerous Caribbean islands, including Hispaniola and Cuba, and reached the coasts of Central and South America. In recognition of his achievements, the Spanish monarchs Isabella I of Castile and Ferdinand II of Aragon, through the Capitulations of Santa Fe, granted him the prestigious titles of Admiral of the Ocean Sea, Viceroy, and Governor of the Indies, although his authority over the new territories was later diminished.