When you step into Florence, Italy’s city hall, you will see a giant painting of soldiers on horses, riding in battle. The picture, Giorgio Vasari’s “The Battle of Marciano,” was commissioned half a century ago as part of a renovation to the building, but what possibly lurked beneath has been puzzling art scholars for years. Rumors that a 500 year old Leonardo fresco lie behind the walls have been swirling, and now it looks like the proof has been found.

The National Geographic society commissioned a search for the lost Leonardo.

Reuters reports:

Researchers used tiny, medical-style endoscopic probes and other high-tech tools inserted through existing cracks in the outer wall holding the Vasari fresco and took samples of substances.

“We found traces of pigments that appear to be those known to have been used exclusively by Leonardo,” said Maurizio Seracini, an engineer and expert in art diagnostics who has been on the trail of the “Lost Leonardo” for three decades.

It is believed that the renovators knew they were covering up a Leonardo painting, and rather than destroy it, they built a wall in front of it. It’s possible that the original painting is still preserved behind the wall. Now the problem is figuring out how to get to it.