In the ruins of a city that was once Rome’s neighbor, archaeologists last summer found a 1,000-pound lead coffin.

Who or what is inside is still a mystery, said Nicola Terrenato, the University of Michigan professor of classical studies who leads the project—the largest American dig in Italy in the past 50 years.

The sarcophagus will soon be transported to the American Academy in Rome, where engineers will use heating techniques and tiny cameras in an effort to gain insights about the contents without breaking the coffin itself.

“We’re very excited about this find,” Terrenato said. “Romans as a rule were not buried in coffins to begin with and when they did use coffins, they were mostly wooden. There are only a handful of other examples from Italy of lead coffins from this age—the second, third or fourth century A.D. We know of virtually no others in this region.”

University of Michigan News Service: An archaeological mystery in a half-ton lead coffin