When Spanish explorers in the early 16th century set eyes on the Aztec capital Tenochtitlan, today Mexico City, they were amazed by what they found -- a beautiful city, larger and more impressive than  most European cities of that era. This city of magnificently adorned edifices,  wide avenues, vast esplanades, open-air markets and astonishing temples was the  commercial and ceremonial center of a civilization that could already trace its  history some 3,000 years.

These same structures were soon razed to make way for others of Spanish influence, the changing landscape reflecting the  changing realities of life in the New World. Yet, in spite of the conquistadors'  best efforts to destroy Mexico's pre-Hispanic past, it is still very much alive  among the more than 20 million native Mexicans around the country who preserve their ancient traditions, and speak nearly 60 languages and dialects, and in numerous archaeological sites. Found throughout the country, these enduring  monuments belong to Mexico's varied pre-Hispanic civilizations, though by far  the best known are those built by the Maya.