Final answer:
The island where the Spaniards built el Fortán de la Navidad is known as Hispaniola, now divided between Haiti and the Dominican Republic.
Step-by-step explanation:
The indigenous name of the island where the Spaniards built the Christmas Fortress (el Fortán de la Navidad) is Hispaniola. This island is significant in history as the site where Christopher Columbus made contact with the inhabitants and established a settlement after his ship, the Santa Maria, ran aground on December 25, 1492.
Hispaniola, which is the island now divided into the countries of Haiti and the Dominican Republic, was originally inhabited by the Taíno people of the Arawak tribe. The impact of Columbus's arrival was profound, leading to the colonization of the island by Spain and subsequent subjugation and enslavement of its native people.