To one side of Mexico City’s enormous central plaza, the Zócalo, stands one of the most astonishing archaeological digs of the last 35 years.

It was originally believed that the huge cathedral in the Zócalo was built directly above the Templo Mayor, the huge Aztec temple at the center of their capital, Tenochtitlan. This was discovered to be false when, in 1978, some electrical workers digging for the metro about 20 yards from the perimeter of the cathedral unearthed by chance a monolith of Coyolxauhqui, the Aztec moon goddess. This discovery led the president of Mexico to authorize the Templo Mayor Project. Over the subsequent 32 years of excavations, digs revealed 13 levels of construction dating from 1375 to 1519.

I arrived early in the morning before the inevitable line began to form. Aztec dancers in native dress perform traditional rituals for tourists as one approaches the Templo Mayor from the Zócalo.

Walking alongside what remains of the temple, I was struck by the stark evidence of the subjugation of one culture by another. The ruins are not as immediately impressive as several other sites in Mexico, specifically because the Spaniards destroyed the huge outermost temple and used the stones to build their grandiose cathedral that overlooks the square. Despite the reduction in scale, the significance of the site cannot be overemphasized. There are layers of temples underneath spanning hundreds of years.

The Templo Mayor was the largest and most important temple. The spot was a sacred one to the Aztecs. According to their tradition, the Templo Mayor represents where the god Huitzilopochtli gave the people the sign that they had reached the promised land, the chosen spot to build Tenochtitlan: an eagle on a nopal cactus with a snake in its mouth. This symbol appears on the Mexican flag.

I was continually engaged by the realization that human sacrifices occurred here. The stepped pyramid’s double staircase remains, marking the spot where the blood of the human sacrifices was spilled. The body was thrown down the stairs after the heart was ripped out. This spilling of sacrificial blood reenacted the death of the goddess Coyolxauhqui at the hands of her brother Huitzilopochtli, symbolizing the duality between night and day, male and female. The Aztecs believed this tension perpetuated the cycle that sustains mankind. Hernando Cortes and the Spaniards apparently did not agree, demolishing the pyramid as an abomination.

The ominous racks of human skulls prominent in the ruins draw further attention to the human sacrifices that were enacted here to please the gods. This area, in the shadow of the temple, was once a plaza where civic and recreational activities took place. Objects and animals were also buried here as offerings to the gods.

Despite the frequent sacrifices, researchers now believe the Aztecs were not as bloodthirsty as the Spaniards depicted them. Some accounts of vast numbers of sacrifices are believed to be exaggerated. The Aztecs were not alone in the practice of human sacrifice – it was also prevalent in other cultures throughout Mesoamerica as a metaphysical sense of indebtedness required to sustain the universe. There are accounts by historians that the Aztecs were conflicted and even troubled by these practices.

The cathedral towers in the background serve as a constant reminder of the clash of cultures and ultimate victory of the Europeans. Tenochtitlan, now Mexico City, was once an island surrounded by the water of Lake Texcoco. This was a microcosm of how the Aztecs imagined the universe. After their conquest and destruction of Tenochtitlan, the Spanish subsequently drained the water to control flooding.

The museum adjoining the ruins helps one imagine how the site must have appeared when the Spanish arrived in 1519. There’s a representation of what the temple may have looked like, and you’ll be rewarded with the best collection of Aztec artifacts anywhere. More racks of gleaming skulls are on display. The more recent discoveries remind you that this is still an archeological site in progress.

The most prominent exhibit in the museum is the recently dug 12-ton stone of the earth goddess, Tlaltecuhtli. It was discovered in 2006 and underwent a 3-year restoration process, sharpening its original ocher and red pigments.

There are undoubtedly more fascinating artifacts to be discovered. Historical records say the remains of three Aztec rulers were cremated and their ashes buried at the foot of the Templo Mayor, but these have yet to be uncovered.

Before visiting the museum and the Templo Mayor site, you may want to stroll over to the adjacent Palacio Nacional to view the impressive murals by Diego Rivera up the staircase from the courtyard. They provide a striking visual representation of the events that took place during this period. I recommend seeing the murals first, as then the impact of the Templo Mayor on the imagination will be intensified.