National Geographic has the scoop:
Over the centuries, Jerusalem’s Church of the Holy Sepulchre has suffered violent attacks, fires, and earthquakes. It was totally destroyed in 1009 and subsequently rebuilt, leading modern scholars to question whether it could possibly be the site identified as the burial place of Christ by a delegation sent from Rome some 17 centuries ago.
Now the results of scientific tests provided to National Geographic appear to confirm that the remains of a limestone cave enshrined within the church are remnants of the tomb located by the ancient Romans. Mortar sampled from between the original limestone surface of the tomb and a marble slab that covers it has been dated to around A.D. 345. According to historical accounts, the tomb was discovered by the Romans and enshrined around 326.
Until now, the earliest architectural evidence found in and around the tomb complex dated to the Crusader period, making it no older than 1,000 years.
While it is archaeologically impossible to say that the tomb is the burial site of an individual Jew known as Jesus of Nazareth, who according to New Testament accounts was crucified in Jerusalem in 30 or 33, new dating results put the original construction of today’s tomb complex securely in the time of Constantine, Rome’s first Christian emperor.