Complex sentence: Pedro de Ursúa (1526--1561) was a Spanish conquistador who is best known for searching the Amazon region for El Dorado and the Omaguas with Lope de Aguirre.
Split into simpler sentences: Pedro de Ursúa (1526--1561) was a Spanish conquistador in the 16th century. Ursúa also searched the Amazon region for El Dorado and the Omaguas with Lope de Aguirre.