as a "witness" to Peter's death. It is one of several ancient Obelisks of Rome. According to tradition, Peter's remains were buried just outside the Circus, on the Mons Vaticanus across the Via Cornelia from the Circus, less than from his place of death. The Via Cornelia was a road which ran east-to-west along the north wall of the Circus on land now covered by the southern portions of the Basilica and St. Peter's Square. A shrine was built on this site some years later. Almost three hundred years later, Old St. Peter's Basilica was constructed over this site. The area now covered by the Vatican City had been a cemetery for some years before the Circus of Nero was built. It was a burial ground for the numerous executions in the Circus and contained many Christian burials because for many years after the burial of Saint Peter many Christians chose to be buried near Peter. In 1939, in the reign of Pope Pius XII, 10 years of archaeological research began under the crypt of the basilica in an area inaccessible since the ninth century. The excavations revealed the remains of shrines of different periods at different levels, from Clement VIII (1594) to Callixtus II (1123) and Gregory I (590–604), built over an aedicula containing fragments of bones that were folded in a tissue with gold decorations, tinted with the precious murex purple. Although it could not be determined with certainty that the bones were those of Peter, the rare vestments suggested a burial of great importance. On 23 December 1950, in his pre-Christmas radio broadcast to the world, Pope Pius XII announced the discovery of Saint Peter's tomb. Old St. Peter's Basilica Old St. Peter's Basilica was the fourth-century church begun by the Emperor Constantine the Great between 319 and 333 AD. It was of typical basilical form, a wide nave and two aisles on each side and an apsidal end, with the addition of a transept or bema, giving the building the shape of a tau cross. It was over long, and the entrance was preceded by a large colonnaded atrium. This church had been built over the small shrine believed to mark the burial place of St. Peter, though the tomb was "smashed" in 846 AD. It contained a very large number of burials and memorials, including those of most of the popes from St. Peter to