The Spanish Engineer Who Drew a Grid on the Bones of Tenochtitlán

The Aztec capital of Tenochtitlán fell to the combined Spanish and Indigenous army of Hernán Cortés on 13 August 1521, after a seventy-five-day siege that had destroyed most of its infrastructure, killed perhaps a hundred thousand of its inhabitants, and broken the political-military authority of the Triple Alliance forever. Approximately seventy thousand survivors emerged from the rubble and surrendered through the causeways. The city Cortés had described in his 1519 letters to Charles V as larger and more orderly than any city in Spain was a smoking ruin.

The decision Cortés took in the weeks following the surrender was not obvious. The conventional Spanish colonial practice would have been to abandon the destroyed indigenous capital and found a new colonial city on dry ground at the lake’s edge. Tenochtitlán sat on an artificial island connected to the shore by three long causeways; its water supply ran along a separate aqueduct from the freshwater springs at Chapultepec; its agricultural base was the system of chinampa floating gardens along the lake. None of the supporting infrastructure was guaranteed to survive Spanish administration. Building a new colonial Mexico City on the shore would have been simpler.

Cortés decided to rebuild on the island. The reason he gave at the time was symbolic — the conqueror’s right to occupy the political-religious center of the defeated. The reason that subsequent administrators repeated was strategic — Tenochtitlán’s island position was the most defensible in the Valley of Mexico. The result was that the colonial capital of New Spain, the city that would eventually become the largest metropolis in the western hemisphere, was built directly on top of the destroyed indigenous capital.

Alonso García Bravo

The man Cortés commissioned to design the new city was a Castilian surveyor named Alonso García Bravo, born around 1490 in Ribera del Fresno, Extremadura. García Bravo had crossed to the Indies around 1513 and had practical experience in the founding of Veracruz (1519) and several Caribbean settlements. He arrived at the ruins of Tenochtitlán in the late autumn of 1521.

His task was unusual. The Aztec city he was redrawing was not abandoned — substantial Indigenous neighbourhoods on the periphery survived more or less intact and would need to be incorporated. The lake-water grid of the original city was substantially preserved in the streets and canals of the post-siege ruin; García Bravo could see the existing layout from any rooftop. The decision he and Cortés made was to retain the rough geometry of the original Aztec city while substantially expanding and Europeanizing the central administrative district.

García Bravo’s surviving plan — the Traza de Alonso García Bravo, c. 1523 — laid out the colonial centre as a fourteen-block grid measuring approximately 700 by 1,100 metres. Its central square (the Plaza Mayor, now called the Zócalo) was sited directly over the destroyed Aztec ceremonial precinct. The new cathedral was projected on the foundations of the Templo Mayor. The viceregal palace was sited over the destroyed Palace of Moctezuma. The municipal administration building was sited over the destroyed Palace of Axayácatl. The Spanish colonial elite occupied the central blocks of the traza; Indigenous residential areas were assigned to peripheral wards (barrios) around the urban core.

The deliberate symbolic point of the layout was that the Spanish administrative-religious centre was identical with the Aztec administrative-religious centre. The geographical core of the new colonial capital had not moved. The political-religious system that occupied it had been replaced.

Burial

The destruction of the Templo Mayor took several years. The Spanish administration ordered the systematic demolition of the temple pyramid through the 1520s; portions of the stone were repurposed as building material for the new cathedral, the new palaces, and the dozens of new Spanish religious houses that proliferated through the colonial centre in the second quarter of the 16th century. By approximately 1550 the pyramid was no longer visible above ground.

The platform on which it had stood was paved over for the new cathedral construction beginning in 1573. The first colonial cathedral was modest; expansion began in 1626 and was not completed until 1813 — a 240-year construction program that buried the foundations of the Templo Mayor beneath progressively heavier ecclesiastical architecture. By the late colonial period, the existence of the Templo Mayor was a matter of historical tradition rather than visible evidence. There was dispute, by the early 20th century, about whether the pre-Spanish ceremonial precinct had been located in the Zócalo at all or in some other adjacent part of the colonial centre.

The 1913 excavations of Manuel Gamio at the corner of Calles Seminario and Guatemala — directly behind the cathedral — recovered portions of the southwestern Templo Mayor base. Gamio’s work was the first archaeological demonstration that the pyramid had survived under the colonial pavement. Subsequent excavations through the 1920s and 1930s recovered more material but could not extend across the colonial city block because the Spanish-period buildings above remained in active use.

21 February 1978

The recovery of the full Templo Mayor occurred by accident. On the morning of 21 February 1978, workers of the Mexico City electrical utility — laying new underground cables in an alley behind the cathedral — broke through a thick layer of colonial paving and exposed a large carved stone disc roughly three metres across. The carving showed a dismembered woman in low relief, surrounded by the disassembled limbs of her own body.

The workers stopped immediately. The Instituto Nacional de Antropología e Historia was notified within hours. The disc was identified within days as the Coyolxauhqui stone — the central Aztec religious sculpture depicting the moon goddess defeated by her brother Huitzilopochtli, traditionally located at the foot of the western stairs of the Templo Mayor. Its presence at the precise alignment archaeologists had long predicted confirmed that the temple’s foundations were still in place beneath the colonial city block.

The Mexican government authorized the systematic excavation of the entire block. The Spanish-period buildings on the site — most of them privately owned 18th- and 19th-century commercial structures — were expropriated and demolished. The Templo Mayor archaeological project under Eduardo Matos Moctezuma has now excavated approximately seven distinct construction phases of the original pyramid, recovered approximately 7,000 individual offerings buried within and beneath it, and produced one of the most thoroughly documented urban archaeological sites in the Americas.

The visible city

The result is the present geometry of central Mexico City: the colonial Spanish cathedral and Zócalo above ground; the excavated Aztec Templo Mayor immediately behind the cathedral, exposed at the original 1521 ground level approximately four metres below modern street level; and the modern 20th-century city above and around both, with the original García Bravo grid still visible in the street pattern of the city’s Centro Histórico. The city continues, in 2024, to be the largest in North America — population approximately twenty-two million in the metropolitan area, built on a drained lake bed whose surface is sinking at approximately one centimetre per year as the groundwater is extracted.

The destroyed Aztec capital and the colonial Spanish replacement and the modern Mexican capital are not three successive cities. They are three layers of the same one.