For almost three thousand years Mexico was the site of some of the most advanced Indian civilizations, most notably the Aztec and Mayan. In many ways, these civilizations were more advanced than their European contemporaries, especially in such spheres as astronomy, mathematics, and city organization. Upon seeing the Aztec capital, Tenochtitl n, for the first time, Spanish explorer Bernal D az del Castillo was awed by its beauty and confessed he had never seen a city in Spain that could match it. However, D az del Castillo's arrival coincided with that of Hern n Cort s, the Spanish conqueror of Mexico who captured the Aztec capital in 1521. Since then, it has been known as Mexico City.