1 WHAT ARE CITIES? Downtown Mexico City, the largest city in the Americas, February 21, 1978: Electrical workers are at work laying a cable on a busy street corner. Suddenly a loud clank resonates from the tip of a laborer's shovel. Kicking away the surrounding dirt, he realizes the edge of the stone he has struck is round and far too huge to dislodge. He calls over his fellow workers to help out. Further digging reveals a portion of a carved arm, then an upturned face five times bigger than life, with a tasseled headdress adorned with bells. Archaeologists from the nearby National Institute of Anthropology and History are called in. Jumping into the pit, they quickly abandon the shovels and get to work with their trowels and whisk brooms so as not to damage the delicate carving. They employ dental picks and toothbrushes to chip away caked-on dirt.

The archaeologists had found evidence of an ancient city, Tenochtítlan, that grew, thrived, flourished, and was destroyed on the turf where modern Mexico City stands today. Over four hundred years earlier, Bernal Diaz del Castillo, a soldier accompanying Hernando Cortés, wrote on seeing Tenochtítlan for the first time: "[A]ll around me there are great towers and buildings rising from the water, all built of masonry. I do not know how to describe it, seeing things that had never before been heard of or seen before nor even dreamed about." It's difficult to reconcile Bernal Diaz's awe over a vast, teeming city with a place that has been reduced to ruins, almost undetectable under the streets of Mexico City. Yet there are other examples of ancient cities that once existed before European settlers ever reached America's shores. In the Americas, cities have grown up, flourished, and died for three thousand years. Centuries before our modern cities appeared, great cultural centers flourished in what is now the American Midwest, Mexico, and the Andes of South America. The excavation of the Coyolxauhqui Stone, found in 1978 at the foot of the Great Temple (or Templo Mayor) stairway, part of the Aztec capital, Tenochtítlan.

The first American cities rose and fell long before our contemporary urban areas blossomed, but they all created lasting works that impress us to this day-tall buildings, huge monuments, exquisitely decorated architecture, beautiful paintings, and spectacular sculpture. Some ancient cities developed writing, literature, and mathematics. Like Boston, Seattle, Los Angeles, Vancouver, and Lima today, America's ancient cities were style setters, symbols of what it meant to be modern and creative. Each developed a great tradition that was maintained for a long time, a way of living that affected and transformed many of the cultures they came in contact with. Their people embraced ideas and customs that seem very different from our own, but there is much to be learned from the ruins of their courts and temples, streets and fortifications-even the everyday articles of the people, rich and poor, who once lived there. The many people who have inhabited our planet before us left a lasting impression on the world, and we can benefit from their knowledge. If we look closely enough, we can discover where they succeeded and why they failed. That's the lesson of history.

CAHOKIA Five hundred years before Christopher Columbus's arrival, Cahokia was the biggest city in North America. One of the many cities of the Mississippian culture, this metropolis was made up of more than three thousand structures. Monk's Mound, the highest of them all, rises up to seventy-five feet (about five stories in a modern building). And yet this lost city lay overgrown and undiscovered until the eighteenth century. When the American explorers Meriwether Lewis and William Clark crossed the Mississippi River going west in 1804, they spotted a tiny Indian village just south of where St. Louis is located today. Clark's diary for September 23 reads: "[We] descended to the Mississippi and round to St. Louis, where we arrived at twelve o'clock; and having fired a salute, went on shore and received the heartiest and most hospitable welcome of the whole village.

" When they stepped ashore, they noticed that the shoreline was strewn with lots of broken pottery and pieces of flint arrowheads, indicating that people had already inhabited those lands. Because they were preoccupied by this social occasion, they had little time to explore the land farther from the riverbank. What they missed, hidden deep in the brush, was a massive building covering an area of fourteen acres (that's bigger than twelve soccer fields!). The French explorers Jacques Marquette and Louis Joliet, who made that same crossing more than one hundred years earlier, had missed seeing the lost pyramid, too. The explorers failed to recognize the great pyramid on the Mississippi because even though it stands out in the landscape, the pyramid is made of earth. It doesn't have any stone facing like Egypt's pyramids and it isn't covered over with stucco and painted in bright colors like the Mexican pyramids, so it was easy to mistake it for a natural hill. By the time President Thomas Jefferson's good friend, the explorer Henry Brackenridge, arrived in the area in 1811, he knew what he was looking for. Brackenridge had heard that there were many Indian mounds situated on the edge of the Mississippi/Missouri floodplain, or bottomlands.

He knew that a spot near the intersection of two of America's great rivers would have been an excellent place to build a city. The location offered great soil for planting and a watery highway for trading goods. As he hacked his way inward from the shore through the cedar- and willow-covered bluffs, Brackenridge noticed that the mounds got bigger and bigger and they were regularly spaced. He had a strong feeling that he was about to arrive at some very important ancient place. Suddenly, he found himself standing in front of the huge earthen pyramid. He had discovered ancient Cahokia! Awestruck, he would later write to the president: "I was astonished that this stupendous monument of antiquity should have been unnoticed by any traveler." He named it Monk's Mound after a group of French monks who had built a monastery nearby. Let's turn the Cahokia clock back a thousand years and try to imagine what Monk's Mound looked like in AD 1000.

The earthen structure supported a huge pole and thatch temple, likely the residence of an elite class of rulers. The grass roof of the temple was decorated with wood carvings of animals covered with feathers. The great pyramid had a two-hundred-acre plaza in front of it, surrounded by a stockade made out of twenty thousand twelve-foot-long logs. That alone would have taken a crew of one hundred workers twenty years working eight hours a day to build-without a day off! TENOCHTÍTLAN AND THE AZTECS More than a thousand miles south of Cahokia, underneath modern Mexico City, lie the ruins of another great native American city, Tenochtítlan, the ancient capital of the Aztecs. We know more about what life was like when that city flourished more than five hundred years ago than we do about any ancient American city. That's because, unlike the people of Cahokia, the Aztecs of Mexico have left us a picture record of their history in addition to magnificent ruined temples made of stone. Before the arrival of the Spaniards, the Aztecs made books, called codices , out of deerskin. These books told stories about the founding of their city, how they worshipped their gods, the history of their wars, and the lives of their rulers.

After the conquest of Mexico by Spain in the sixteenth century, priests who came to the New World to convert the Aztec people to Catholicism interviewed Aztec officials and acquired further details about daily life. Scribes and artists continued to create codices during the colonial period. At the time of Spanish contact, Tenochtítlan was one of the largest cities in the world-more than fifty thousand people made their homes there. Unlike the first explorers who visited Cahokia, the first outsiders to view Tenochtítlan saw a real live "downtown pyramid" in a bustling city. There were many temples, altars made of stone for worshipping a host of Aztec deities, schools, marketplaces, and ball courts. Seeking gold, the Spanish conqueror Hernando Cortés docked his ship in Veracruz on the Gulf of Mexico in 1519. Accompanied by a few hundred men, a few dozen horses, and warriors from tribes who considered themselves enemies of the Aztecs, Cortés climbed the pass between the snowcapped twin volcanoes called Popocatépetl (the man) and Ixtaccihuatl (the woman). It was there that Cortés first cast his eyes upon the Valley of Mexico below him.

He glimpsed Tenochtítlan, the great city situated on an island in Lake Texcoco and connected to the mainland by four causeways. Seeing the gleaming palaces with exquisite gardens and waterways, one of his soldiers wrote in his diary: "[T]here is a building of such height and beauty that it astonishes me … the equal in cut stone of any I have seen in Seville, and all around there are eleven or twelve more just like it all closely clustered together." For the first time, outsiders were glimpsing an American city that rivaled the great urban centers of Europe. CUZCO When Francisco Pizarro and his army landed on the west coast of South America in 1532 and penetrated the high Andes to reach Cuzco, they, too, were awed by what they saw in this equally large city. It had taken them several weeks to reach the city,.