The discovery of an ancient wall beneath a Paris hospital may have answered a question archaeologists have been arguing about for decades: Where, exactly, did Paris begin?

The 72-foot stone-and-wood wall turned up this summer during construction at the Hôtel Dieu hospital on the Île de la Cité, the island in the Seine that sits at the center of modern Paris, according to the New York Times. Archaeologists also found a Gallic spearhead nearby. Carbon dating puts the wall somewhere between 200 BCE and 10 BCE, right around the period when Rome was conquering Gaul.

In his account of the Galic Wars, Julius Caesar wrote about a place called Lutetia, a settlement built by the Parisii, the Gallic tribe that eventually gave Paris its name. Caesar described Lutetia as a fortified town on an island in the Seine, and wrote that its inhabitants burned the settlement and destroyed its bridges as Roman troops approached. Regardless, Rome conquered it in 52 BCE.

For a long time, though, archaeologists weren’t sure Caesar’s geography could be trusted. There wasn’t much physical evidence of a major Gallic settlement on the Île de la Cité, while digs in Nanterre, west of Paris, turned up plenty. By the 1990s, some scholars had come to believe that ancient Lutetia was actually there.

This wall changes the calculus. Matthieu Poux, an archaeology professor at the University of Lyon II who had been among those skeptical that Lutetia was on the Île de la Cité, told the Times the find changed his mind. He now has “no doubt” that the ancient city was there.

There’s also a particularly tantalizing detail: the wall was burned. Archaeologists found charred seeds and the remains of a burned wooden building nearby, which at least raises the possibility that they’ve found physical traces of the destruction Caesar described more than 2,000 years ago. Researchers aren’t ready to make that claim yet; the French culture ministry says more work is needed to establish exactly when the wall was built and what it was used for.

Still, the find fills in massive blank in the history of one of the world’s most excavated cities. Archaeologists know quite a bit about Roman Paris, including settlements beneath today’s Latin Quarter and Luxembourg Gardens. Gallic Paris has been much harder to pin down. Poux said this single excavation had increased the available evidence on the subject “tenfold.”

Further excavations are planned around the hospital, and the wall will eventually be removed so it can be studied and displayed.