An ancient stone circle sits on the summit of a mountain overlooking the Cajamarca Valley in Peru’s northern highlands. At first glance, it doesn’t appear particularly remarkable — just a circle about the size of a convenience store, with a smaller circle inside. Meanwhile, what remains of its borders are made up of standing boulders.

But new research has revealed that this unassuming plaza dates back nearly five millennia, to an era that far preceded the Inca and their predecessors, like the Wari and Chimú cultures. In fact, this ancient stone plaza, which was likely used as a space of ceremony or ritual, predates some of the oldest grand Andean constructions like Chavín de Huántar by nearly 2,000 years.

What’s more, the plaza’s discovery reveals more about the people that first began to build other stone plazas, like these across the Andes and the central Peruvian coast.

“Even at a very early stage, people throughout the Andes were in contact, and they were in contact enough to share these ideas of the right way to build a ritual plaza,” says Jason Toohey, an archaeologist with the University of Wyoming who worked on dating the stone plaza in the Cajamarca region. “Maybe they were sharing whatever types of events took place in them.”

Digging into the Cajamarca Stone Circle

Toohey has been excavating in the area around the Cajamarca stone circle since about 2015, at a larger archeological site known as Callacpuma. This roughly 250-acre site includes a number of settlements that date to different ages.

“We have every time period of the Cajamarca culture right up until the colonial period,” Toohey says.

Read More: Unraveling the Mysterious Traditions Within Chavín de Huántar

The stone circle sits on a summit near this site. It wasn’t lost or buried — Toohey stresses that he and his colleagues weren’t the ones to first discover it. “Local people had considered this to be a special place for a long time,” he says. “Occasionally, people would go up there to bury their offerings.”

Still, Toohey was surprised by their research findings, published in Science Advances in 2024. Radiocarbon dating of material at the base of some of the megalithic stones revealed that the rocks date back as far as 2750 B.C.E.

“[That’s] much, much earlier than I thought,” says Toohey.

Archaeologists still don’t know much about the Cajamarca plaza; they haven’t found other remains dating back to the same period that reveal much about the people that put them up in the first place. But Toohey says the plaza’s construction may have represented a turning point in the Andes, when nomadic people began to become more sedentary and experiment with planting.

Another theory is that these standing stones may have been a way of claiming land or resources, Toohey speculates. Or, the plaza might have represented a broader form of social cohesion than had been previously seen before.

How Did Ancient Andeans Use the Cajamarca Plaza?

In any case, the Cajamarca plaza would have taken people several weeks to build, Toohey says. The plaza itself may have been used for ceremony or ritual, though without further evidence much remains a mystery. Toohey says that the people that did use it probably remained somewhat nomadic for another half millennium or so.

Still, Toohey’s team did find arrow points that date earlier than the stone circle, but they haven’t found anything that looks like permanent dwelling places in the area near the plaza’s construction.

“They certainly weren’t living there full-time,” he says.

Read More: How Hunter-Gatherers Used The Land Around Stonehenge

While similar to other circular stone plazas in some ways, the Cajamarca structure is also slightly different. Whereas plazas elsewhere are typically sunken, with fitted masonry walls, the circle at Cajamarca sits on the surface, with individual stones standing upright. While much smaller — with boulders standing nearly 5 feet tall, at most — it bears resemblance to structures like Stonehenge, which was built around the same time.

Subtle differences aside, there’s still likely a link between the Cajamarca circle and those at places like Caral. “My suspicion is that this plaza is somehow connected to this broader tradition, but it’s also an offshoot,” Toohey says.

The fact that it wasn’t sunken may not be a question of stylistic difference from other sunken plazas so much as just convenience —the bedrock is very close to the surface here, meaning it would have been difficult to dig down further.

Moving forward, Toohey’s team will continue to search for more evidence in an effort to learn more about the people that built it. “This just adds one more layer, one more puzzle piece of this much broader study of these plazas,” he says.

Read More: Does the Grand Civilization of the Inca Empire Still Exist Today?

Other Ancient Andean Stone Plazas

The stone plaza in Cajamarca isn’t the only one that dates to this ancient period in Andean civilization. Archaeologists have excavated several of these megalithic stone circles. The earliest of these dates back to about 3100 B.C.E. — more than 5 millennia ago. Most of these structures are sunken into the ground, built with a number of large stones that interlock together with some sort of plaster connecting them.

These stone circles include famous examples at places like Caral, just north of Lima, Peru. Caral is one of the oldest urban areas in the Americas, the beginnings of which date back to about 3000 B.C.E. The circular sunken plaza at Caral dates to about 2600 to 2550 B.C.E., Toohey says, about 100 years later than the stone circle in Cajamarca.

Still, other sunken stone plazas can be found in the Andes, and some in the central coastal region of Peru. Andean people continued to build them until the one at Chavín de Huántar, which may date to abound 500 B.C.E.

“The plaza at Chavín, it’s one of the most recent of them, and certainly one of the best known since it sits at that amazing site,” Toohey says.

Read More: Is Caral, Peru, the Oldest City in the Americas?

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