Cahokia

Around 1000 CE, a complex metropolis thrived near present-day St. Louis, near the Mississippi, Missouri, and Illinois rivers.

The city was dominated by at least 100 raised structures, which were topped with houses, burial mounds, and other buildings.

Little is known about this ancient civilization. But based on historians' research, it was a cosmopolitan center of crafts, trade, and architecture.

Teotihuacan

Located just 30 miles (48 km) northeast of present-day Mexico City, Teotihuacan was possibly the largest city in the Americas.

It's estimated that more than 100,000 Teotihuacanos lived in the impressive city, filled with avenues, temples, palaces, and thousands of apartment buildings.

Then there was also the Pyramid of the Moon, which was used for ritual sacrifices of animals and humans. Archaeologists have found proof beneath it, including the remains of wolves, eagles, pumas, and 12 human bodies.

Chaco Canyon

From 800 to 1200 CE, indigenous people lived in more than 150 settlements around Chaco Canyon, located in modern-day New Mexico.

The Chacoan people were farmers and traders. To water their corn, squash, and beans, they harnessed the intermittent flow of local streams through canals and ditches.

With no written language, much of what is known about the Chacoans comes from their burial sites. One found burial held 13 presumably high-ranking bodies, which DNA analysis showed were related through their mothers or grandmothers. This means power may have been passed down through the maternal line.

By the 13th century, the Chacoan people began to leave for other parts of the Southwest. This was possibly due to severe drought.

Etzanoa

By the Walnut and Arkansas rivers, near present-day Arkansas City, once flourished a vast metropolis of more than 20,000 citizens.

During the cold winter months, the locals would follow the bison herds and build temporary homes while traveling.

In the late 16th century, Spanish conquistadors came in contact with the group living in the region. But what was a friendly encounter quickly turned. In 1601, the Spanish took hostages and the residents ran away.

Spiro Mounds

In 1933, treasure hunters stumbled across a burial chamber near Spiro, Oklahoma, which had been closed for 500 years. Inside they discovered stunning treasures.

Apart from the treasures, archaeologists managed to uncover an area that belonged to a prehistoric power. It equaled the size and sophistication of the Aztec and Inca.