In the country of Mexico, is the ancient city of Teotihuacán. This city is famous for its enormous stone pyramids. Archaeologists have discovered a secret tunnel beneath one of the most famous pyramids.

Hidden Tunnel
This pyramid is called the Pyramid of the Moon. For nearly 2,000 years, the tunnel has remained hidden beneath it. The Pyramid of the Moon is the second-largest building in the ancient city.

Sources claim the largest city structure is the Pyramid of the Sun. The archaeologists who discovered it believe that the tunnel looks similar to other Teotihuacán monuments. The tunnel may represent the underworld of the belief system of the Teotihuacán people. This 2,000-year-old group was around before Christopher Columbus arrived in the Americas. They are even thought to have come before the Aztec people, who later lived in the area.

In the middle of the city is a central square called Plaza de la Luna, or "plaza of the moon." From there, a secret passageway extends from the plaza to the Pyramid of the Moon. It is buried 10 meters (33 feet) deep, nearly the length of a school bus. The underground passage is similar to other tunnels that have been discovered. Archaeologists recently found a tunnel under the Temple of the Plumed Serpent too.

Scanning Below Earth's Surface
No one has been able to go inside the tunnel yet. The discovery was made by a team of archaeologists while they were studying the city central square. They were using a special technology that allows them to look below Earth's surface. This technology is called electrical resistivity tomography. It measures the shapes and distances under the ground.

The team of archaeologists from Mexico was studying the site to learn how to better protect and preserve the famous central square when they stumbled upon the tunnel.

What Was the Use of the Tunnel?
The Pyramid of the Moon was likely used for human sacrifice and other religious ceremonies. Human remains were found inside of the pyramid tombs. It is unclear what the tunnel may have been used for. Archaeologists plan to further explore the tunnel to determine its purpose and whether or not it contains more artifacts.

Teotihuacán was a major city for many years and had a complicated history. So much of its story has yet to be discovered. It was one of the largest in the Americas during the ancient days. At that time, it was home to at least 125,000 people.