Complex sentence: Spanish explorers recorded this region as New Mexico (' in Spanish) in 1563, and again in 1581, hoping to find there wealthy Mexican Indian cultures similar to those of the Aztec (Mexica) Empire of the Valley of Mexico.
Split into simpler sentences: Spanish explorers recorded this region as New Mexico (' in Spanish) in 1563. The Spaniards hoped to find wealthy Mexican Indian cultures there similar to those of the Aztec (Mexica) Empire of the Valley of Mexico.