NARRATOR: Mexico City.
Beneath the current-day capital of Mexico
lie the ruins of the ancient Aztec metropolis
known as Tenochtitlan.
The Aztecs dominated much of central Mexico from the 14th
to the 16th century AD, and Tenochtitlan
is considered to be their first official settlement--
an incredibly sophisticated city featuring a grid
system of canals and causeways.
But according to their historical texts,
the Aztec civilization did not originate here.
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EDWIN BARNHART: The Aztecs say they
started from this place up in the north called Chicomoztoc.
It was a cave, and inside that cave,
it had seven different caverns.
And there were said to be seven different tribes.
And the Aztecs say they were part of the seven tribes
that came from the seven chambers of Chicomoztoc.
NARRATOR: While Chicomoztoc was once
thought to be a mythological place,
some scholars believe archeological evidence suggests
that it really did exist, and is located
at the site of the ancient pyramid complex
known today as Teotihuacan.
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EDWIN BARNHART: The place of seven caves--
we think maybe that has actually been located archeologically
at the sight of the main temple of Teotihuacan,
called the Pyramid of the Sun, which sits just
north of the valley of Mexico.
Underneath it is actually a cave with seven different spots
that it extends out into, and that's
where the Aztecs said their original ancestors came from.
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NARRATOR: In the 16th century, Spanish chronicler Gerónimo
de Mendieta recorded the legends of the local native population.
According to their accounts, the Aztec
believed that they were fashioned
by a group of stranded gods within these seven caves.
JONATHAN YOUNG: Mendieta wrote an account of Aztec legend.
In this report, he describes a giant flint knife
landing on the earth.
And the earth was trembling and shaking as this enormous flint
knife landed.
Then, some 1,600 gods disgorged from this thing.
And they are responsible for launching Aztec civilization.
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EDWIN BARNHART: The Aztecs talk about the many gods coming down
to earth and creating humans.
They create them out of bone, ash, and their own blood.
And they make them somewhat in their own image,
but they make them specifically so that they will honor them
and they will serve them.
GIORGIO A. TSOUKALOS: All of a sudden,
there is a description of a giant flint
knife that descended from the sky,
and somebody emerged out of it.
One has to wonder whether or not our ancestors
were witness to a landing of some type of a craft.
If so, then the Aztec story suggests
that at some point in our history,
extraterrestrials created mankind.
And something very strange was going on at Teotihuacan.
NARRATOR: Located just 30 miles northeast of Mexico City,
the Teotihuacan complex encompasses nearly eight
square miles, and is dated to the first century A.D.
It is the oldest and most sophisticated
city of Mesoamerica, an area that
extends from northern Mexico down through central America.
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The civilization predated the Maya by at least 100 years.
At its peak, it was said to have supported
nearly 100,000 residents.
It was also the largest city in the entire Western hemisphere
prior to the 15th century, and served
as the major commerce and religious center
for the region.
EDWIN BARNHART: The significance of Teotihuacan
cannot be overstated.
It is the Rome of Mesoamerica.
The things that Teotihuacan did set the pattern for
all other city-states after it.
NARRATOR: The central features of the complex
are two large pyramids, known as the Pyramid of the Sun
and the Pyramid of the Moon, as well
as a temple dedicated to Quetzalcoatl,
the feathered serpent.
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These structures stand alongside a thoroughfare referred
to as the Avenue of the Dead.
Over 200 smaller buildings, platforms, and pyramids
are found adjacent to the avenue,
and there are thousands of living quarters
just outside the complex.
But as incredible as Teotihuacan is,
no one knows exactly who built this metropolis
or what happened to its occupants.
EDWIN BARNHART: Teotihuacan, despite its size,
has no hieroglyphs whatsoever.
There are other cultures in Mesoamerica that
were using writing systems.
There's nothing like that at Teotihuacan.
So we don't really have a clear history of what happened
at Teotihuacan, and we can't really
find evidence of their rulers.
--to develop a complete, huge complex, citadel--
WILL HART: We have such a sophisticated site
that embodies engineering principles, craftsmanship, art.
Where did it originate?
Where are the smaller versions of this?
Well, we don't find any.
So we don't have a progression, an evolution
to show where this came from.
So we have to ask, where did it come from?
DAVID WILCOCK: We've become conditioned
to look at these awesome works of stone architecture
and think, oh, primitive people did that,
and they used primitive methods and primitive technology.
But we have to rethink the fundamental assumptions
and come to a greater and greater level of understanding
that the technology required to build these artifacts, in fact,
is greater than anything that they possessed.