Roman Emperor Caligula built a small circus in his mother's gardens at the base of Vatican Hill, where charioteers trained and where Nero is thought to have martyred the Christians. To crown the center of the amphitheater, Caligula had his forces transport from Egypt a pylon that had originally stood in Heliopolis.
The obelisk, made of a single piece of red granite weighing more than 350 tons, was erected for an Egyptian pharaoh more than 3,000 years ago. In 1586 it was moved to its present location in St. Peter's Square, where it does double duty as a giant sundial.