(CNN)Archaeologists say they've found the long-lost capital of an ancient Maya kingdom near the border between Mexico and Guatemala.

The Sak Tz'i' kingdom was home to between 5,000 and 10,000 people in what is now Chiapas, Mexico, from about 750 BCE to 900 AD, Brandeis University associate professor of anthropology Charles Golden told CNN.

The kingdom wasn't particularly powerful and was surrounded by some of the superpowers of the day, Golden said. He said the Sak Tz'i' kingdom was frequently mentioned in inscriptions found in other cities.

"The reason we know about the kingdom from the inscriptions is because they get beat up by all these superpowers, their rulers are taken captive, they're fighting wars, but they're also negotiating alliances with those superpowers at the same time," he said.

The downtown area was about a third of a mile long and a quarter mile wide (600 meters by 400 meters) and had pyramids, a royal palace, a ball court and a number of houses.

"These are not big empires. They're small city-states trying to carve out their little, little territories," Golden said.

Golden and Brown University bioarchaeologist Andrew Scherer are leading the team that has been excavating the site since 2018. They published their findings in the Journal of Field Archaeology.

Golden said they found out about the site after graduate student Whittaker Schroder got a tip from a street food vendor, who introduced him to the rancher who owned the property.

The rancher had a stone tablet that had an inscription and a drawing of a Sak Tz'i' king dressed as the Maya storm god.