Teotihuacan, translated from the Aztec language as “birthplace of the gods”, or “place where gods were born”, was an important religious and cultural center during the Aztec empire. However, the oldest monuments in the city predate the Aztec empire by at least 300 years.
This archaeological site in modern-day Mexico is famous for its broad central “Avenue of the Dead”, surrounded by a dozen pyramids and platforms. The Pyramid of the Moon was constructed between 200 and 250 CE and is 150 feet high. The nearby Pyramid of the Sun is even higher with 216 feet, but as the Pyramid of the Moon was built on elevated ground, it appears taller.
Archaeologists know that apart the visible large structures, also the underground of the city holds some secrets. In 2003, archaeologists discovered an almost 60 feet vertical shaft beneath the Avenue of the Dead. Excavation revealed a system of tunnels and chambers, also human remains and diverse objects made from green obsidian, a type of volcanic rocks used in religious rituals.
The extent of this tunnel-system remains uncertain to this day. Archaeologists suspected that the tunnels follow the pattern of the streets and pyramids on the surface. As an excavation of the complete site was not possible, in 2017 a team of geologists used electrical resistivity imaging instead to map the underground beneath the Avenue of the Dead. Electrical resistivity imaging is a geophysical technique used also on other archaeological sites to map the composition of the underground, revealing large subterranean cavities or the presence of groundwater. The researchers discovered a tunnel at a depth of 26 feet, that starting from the center of the avenue runs to a 49 feet in diameter large cavity hidden beneath the Pyramid of the Moon.
The age and the use of this network of tunnels and chambers remain uncertain. It is believed that it had a religious significance, as a symbolic gateway to the underworld or as a place for worship at specific springs or holy wells.