For over 1,800 years, the tunnel has been sealed off from the world. The tunnel, which is about 15 yards under the ground and runs for 130 yards, is an amazing find.
The tunnel is located under the Temple of the Snake in the pre-Hispanic city of Teotihuacan, which is about 28 miles northeast of Mexico City.
Researchers at National University in Mexico made the discovery using radar. They said that the tunnel's walls were covered in symbols.
The Researchers hope to explore the tunnel and believe they may find ancient Mesoamerican remains.