What Happened to Teotihuacan?

Teotihuacan, meaning 'the place where the gods were created' in Nahuatl, emerged as a significant urban center in the Mexican Highlands around 100 BCE, with major monumental construction continuing until about 250 CE. By its zenith around 450-500 CE, it was the largest city in the Americas, encompassing some 8 square miles (20-30 km²) and housing an estimated population of 100,000 to 250,000 people, making it one of the world's largest cities at the time. The city's influence spread throughout Mesoamerica, evident in its distinctive architecture, art, and trade networks, particularly its control over valuable obsidian deposits.

The reasons for Teotihuacan's collapse and abandonment, which occurred between 550 and 750 CE, remain a subject of intense scholarly debate. Theories include internal social strife, possibly involving the poor rising against the elite and burning major buildings, as suggested by archaeological evidence of systematic burning and desecration of elite structures along the Avenue of the Dead. Another hypothesis points to external invasion or military conflicts disrupting supply networks. Climate change, specifically severe droughts around 535-536 CE, is also considered a contributing factor, potentially leading to resource scarcity, malnutrition, and population decline.

After its decline, the city lay largely in ruins, though parts were occupied. Centuries later, the Aztecs revered Teotihuacan as a sacred site, believing it to be the origin of civilization and undertaking pilgrimages there. Modern archaeological exploration began in the 19th century, with significant restoration work on monuments like the Pyramid of the Sun in the early 20th century. The site was designated a UNESCO World Heritage Site in 1987, recognizing its outstanding universal value.

Today, Teotihuacan is Mexico's second most-visited archaeological site, attracting over 1.3 million visitors in 2024. Ongoing archaeological research continues to uncover new information. In 2021, 1,800-year-old flower bouquets were found beneath a pyramid. The use of advanced technologies like LIDAR in 2025 has provided new perspectives by revealing buried structures and mapping the impact of human activities on the landscape. The Project Plaza of the Columns Complex undertook its ninth field season in the summer of 2025, continuing to delimit important buildings like Structure 44, which shows evidence of intentional burning near the city's end. In December 2025, the Pyramid of the Moon reopened to visitors, with access restricted to the first level for preservation.

As of 2026, Teotihuacan remains a vibrant center for tourism and research. In February 2026, Mexico announced million-dollar upgrades to archaeological zones, including Teotihuacan, in preparation for the 2026 FIFA World Cup, with discussions underway to potentially reopen the climb to the Pyramid of the Sun. Thousands gathered at the site on March 20, 2026, to welcome the spring equinox, a traditional event. However, on April 20, 2026, a tragic incident occurred where a gunman killed a Canadian woman and injured several others before taking his own life at the pyramids. This event underscores the ongoing challenges of managing security and preservation at such a globally significant site.