London, July 14 : A team of archaeologists are all set to open a long-sealed cave under a Mexican pyramid in the hope that it will unlock the mystery of one of ancient civilization's greatest cities - Teotihuacan.
At its zenith between 150 AD and 450 AD, Teotihuacan was home to up to 200,000 people of various ethnic origins and thought to have been larger than any European city at the time, including Rome.
With its soaring stone pyramids and geometric temples, Teotihuacan was once the biggest city in the Americas and possibly the world.
But, sometime in the 7th or 8th century, it was set ablaze - possibly as the result of an insurrection - and abandoned.
The Aztecs believed the city was divine and identified it with the place where the sun was created.
According to a report in the Telegraph, the tunnel entrance was discovered by accident in 1971 while workmen were installing a sound and light show. After initial tests, it was dismissed as a natural cave and sealed two years later. Hundreds of Mexicans still gather at the Pyramid of the Sun to receive energy from the sun during spring equinox.
However, experts have never been able to say with certainty who built it and why it was suddenly abandoned.
Now, an international team of experts believes the answer may lie under the Pyramid of the Sun, the centre point of the vast ruined city 25 miles outside Mexico City. At the end of this month, they are to investigate a man-made tunnel and cave system underneath the pyramid - the third biggest in the world - to test theories that it was used for rituals including human sacrifice.
"We think it had a ritual purpose. Offerings were placed at the very end of the tunnel as part of the pyramid's construction process," said Alejandro Sarabia, Teotihuacan's director of archaeology.
He will lead a team of Mexican, American and Japanese experts into a 295 ft long, 8 ft high tunnel some 20 ft below the pyramid.
"We want to find out why the Teotihuacan people sealed it and when," said Sarabia. "Excavating the cave could give us some clues about what happened at Teotihuacan, about the fate of the city," he added.
"If we can find out what happened, when, and perhaps how, it will give us a better idea about the history of the Pyramid of the Sun and of the city in general," said Sarabia.
"It may well have been used for sacrificial rites, dancing or other rituals," he addded.
It is believed these burials were part of a ritual dedication of the building while other victims, probably captured enemy warriors, were killed to bring the city good luck.