Massive Mexico City has been a power since at least the 13th century, when the awe-inspiring island metropolis of stone fortresses and lush canals was called Tenochtitlán. It was the seat of the mighty Aztec Empire, a glorious capital known for its architectural splendor, scientific advancement, and cruel religious devotion. 

In 1521, Spanish forces led by Hernándo Cortés laid siege to the city. After a costly victory, they systematically leveled every pyramid and palace, using the stones to rebuild Mexico City in Spain's image. Exactly 300 years later, Mexico declared its independence and, above the Metropolitan Cathedral and vast, stone Zócalo, raised an Aztec flag: An eagle, sitting on a cactus, eating a snake.

This was the sign that Aztec seers were told to find, and upon that spot found their nation. They saw the eagle atop an island in Lake Texcaco, long since drained to slake Spanish thirst. The Aztecs built their Central Plaza on that very spot, today Mexico City's Zócalo, as well as the Imperial Palace palace (now the National Palace) and Templo Mayor, or Great Temple. With the help of a knowledgeable guide, you'll learn to see past the Spanish veneer and into this city's Aztec heart.

Day tours also take in Chapultepec Park, first protected in 1325 and today a fine spot for a family picnic. It is home to the amazing National Museum of Anthropology, a must for anyone interested in Mexico's 30 tumultuous centuries. The neighborhood was once reserved for Aztec royalty, and remains home to some of the city's best hotels.

If you'd like to see what remains of old Tenochtitlán, head to the last liquid remnants of Lake Texcoco, at the southern edge of the city's sprawl. The Hanging Gardens of Xochimilco still raise traditional crops; take a colorfully painted trajinera, or flat-bottomed boat, through Xochimilco’s slow-moving canals and flower-filled islands.

The Aztecs, however, were not the first to settle Mexico's fertile central valley. Just outside their city are the mysterious Pyramids of Teotihuacán, magnificent both their bulk and precise design. This tour also takes in the Shrine of the Virgin of Guadalupe, patron saint of Mexico and the Americas. Early on in the Spanish occupation, she appeared - a young, indigenous girl of perhaps 14 - to Juan Diego, a recent Aztec convert to Christianity. Her image, distinctly Aztec and surrounded by sacred roses, remains one of Mexico's most enduring symbols.