On a blustery day in April, Italian archaeology student Marco Valeri stepped into an archaeological dig at the Cahokia Mounds.

He bent down to adjust a trowel, pointing it north to help orient a photograph of the broken pottery. A blackboard was placed in the frame to indicate the location: Collinsville, Illinois.

At its peak, Cahokia was the epicenter of ancient Mississippian culture. With a population of 20,000 in 1250 A.D., Cahokia was larger than London was at the same time. It had every marking of a large city such as population density and surplus capital: everything but writing, according to an exhibit in the visitor’s center. Now, a group of archaeologists from the University of Bologna in Italy are unearthing the mounds, trying to learn how civilizations develop political complexity.

“I’ve always wondered about this strange place that is Cahokia,” said Davide Domenici, professor at the University of Bologna. Domenici has been visiting and studying these mounds for the past three years. “Usually we archaeologists think that in ancient North America there were fairly simple societies, but Cahokia is actually an example of some kind of political complexity.”

Archaeologists are careful about how they talk about Cahokia’s social context. Few indications at the site today allow researchers to classify the city’s political and social structure with any degree of certainty.

“Can we call it a state, can we call it a chiefdom? We don’t know what to call it, we don’t know what it was,” he said. “But the idea is to study this complexity, and maybe paths to political complexity that were quite different from those we are used to in other parts of the world.”

Cahokia has the largest examples of earthwork north of Mexico, where Domenici has previously done much of his research. At its base, the 100-foot-high Monks Mound takes up over 14 acres--more than the Great Pyramid of Giza, in Egypt, according to the exhibit.

In 2012, the Italian archaeologists found what they believed were public buildings in the plaza west of Monk’s Mound. This year, the plaster and postholes they found during their most recent trip proves them right.

“It’s made the last two weeks worth it,” said Domenici. “A single post bit seems nothing, but when you put all together on a map you start understanding them.”

The students have picked up on a site that researchers left off in the 1960s. The posts they uncovered are evidence of a western wall that closed a palisade compound. Each identified structure is another element to help archaeologists map and decrypt the construct of the Cahokia civilization.

Imma Valese has traveled to the Cahokia Mounds as a student for the past three years. She was excited to help find more pieces of the wall.

“When you have studied for a long time what you are looking for and then they show up,” she said. “It is very amazing.”