This is the supposed tomb of Archimedes, although some scholars say that this tomb dates from a much later period than Archimedes' death here in Siracusa in 212 BC.
Archimedes was killed by a Roman soldier during the Siege of Siracusa.
In 75 BC, Cicero relocated the overgrown tomb, with it's sphere and orb inscription, relating to Archimedes mathematical proof that a the volume and surface area of the sphere is 2/3 that of the cylinder that encloses the sphere.
"But from Dionysius’s own city of Syracuse I will summon up from the dust—where his measuring rod once traced its lines—an obscure little man who lived many years later, Archimedes. When I was questor in Sicily I managed to track down his grave. The Syracusians knew nothing about it, and indeed denied that any such thing existed. But there it was, completely surrounded and hidden by bushes of brambles and thorns. I remembered having heard of some simple lines of verse which had been inscribed on his tomb, referring to a sphere and cylinder modelled in stone on top of the grave. And so I took a good look round all the numerous tombs that stand beside the Agrigentine Gate. Finally I noted a little column just visible above the scrub: it was surmounted by a sphere and a cylinder. I immediately said to the Syracusans, some of whose leading citizens were with me at the time, that I believed this was the very object I had been looking for. Men were sent in with sickles to clear the site, and when a path to the monument had been opened we walked right up to it. And the verses were still visible, though approximately the second half of each line had been worn away." ....Cicero, 75 BCEHoward and Jayne [ Just Imagine ] 10-Jun-2006