Final answer:
The significant achievement of Spanish exploration was proving the existence of the Americas, as Christopher Columbus did in 1492. This discovery opened up new territories for Spanish settlement and imperial expansion.
Step-by-step explanation:
One of the notable achievements of Spanish exploration was proving the existence of the Americas. This was accomplished by Christopher Columbus in 1492, an event that had lasting implications for the world. Following Portugal's earlier exploration efforts, the Spanish sponsored Columbus's voyage, which was initially aimed at finding a new route to Asia. Instead, Columbus landed in the Caribbean, which led to the Spanish claiming vast lands and founding new territories. The Spanish conquest resulted in the establishment of settlements, the extraction of wealth from regions like the Aztec and Inca Empires, and a profound impact on native populations and global trade.
The Treaty of Tordesillas of 1494 was significant in Spanish and Portuguese relations, dividing the newly discovered lands outside Europe between the Kingdom of Spain and the Kingdom of Portugal along a meridian 370 leagues west of the Cape Verde islands (off the west coast of Africa). However, the achievement of exploring and proving the existence of the Americas stands as a monumental outcome of Spanish voyages in the late 15th and early 16th centuries.