A Mayan engineering legacy - Coba.

By 700 A.D., the Mayan city of Coba covered 30 square miles, had an estimated population of 50,000, a 120-foot-high pyramid, and was at the hub of a roadway system connecting it with the other powerful cities of the Yucatan peninsula. Two centuries later, it was left almost abandoned.

Today, scientists are attempting to solve the mystery behind this city that was one of the wonders of Mesoamerica. Approximately 80 miles south of the present-day resort city of Cancun on Mexico's Yucatan peninsula, archaeologists are digging through layers of dense jungle. From the top of the Nohoch Mul, the 120-foot-high pyramid that is the capstone of the city's engineering legacy, they can see some 6500 mounds spread throughout the jungle. Under each mound is a structure that served a purpose in the daily lives of Coba's residents.

Although these ruins were first discovered in 1886, exploration did not begin until the late 1920s and early 1930s. But it was not until 1972 that an organized effort was made by the National Geographic Society in conjunction with the Mexican Institute of Anthropology and History to uncover the city. A program funded by the Mexican government continues to explore and study Coba, but progress has been slow. Dense vegetation covers the ruins, creating the appearance of mounds in an otherwise flat jungle. Although less than 10 percent of the mounds have been excavated, archaeologists are convinced that Coba was one of the largest Mayan settlements on the Yucatan peninsula.

Today's experts have considered whether the engineers of Coba devised an advanced technology to design structures that could stand for more than 1000 years. The evidence of recent digs, corroborated by progress scholars are making in deciphering Mayan glyphs, indicates otherwise. Archeologists believe that the Mayans used neither the wheel nor the pulley and that no beasts of burden lived in the area at the time. Instead, the engineers of Coba used plentiful native labor to construct the very advanced urban center. Coba's pyramids, temples, platforms, and civil works were made of precisely cut limestone blocks from nearby quarries, which were transported to their respective sites exclusively by human labor. The infrastructure could support the population of 75,000.

"In their engineering, architecture, and construction, the Maya simply substituted labor for technology," said Brian Dillon, field archaeologist and professor of archaeology at the University of California at Los Angeles and an expert on the cultures of Mesoamerica. "What they drew upon was the patience and deep-seated work ethic of the Mayan people. "