Every year, millions of pilgrims flock to Jerusalem's holiest site in Christianity, even while nobody today can know for certain if it is really is the place where Jesus Christ was buried and resurrected.

But researchers may be a significant step closer to showing it is indeed the spot after the remains of a limestone cave enshrined within the Church of the Holy Sepulchre in the Old City have proved to be remnants of the tomb located by the ancient Romans, according to the results of scientific tests provided to National Geographic.

It is known that the tomb was discovered by the Romans and enshrined in around 326. Now, mortar sampled from between the original limestone surface of the tomb and a marble slab that covers it has been dated to around AD 345.

Up until now, the earliest architectural evidence found in and around the tomb dated to the Crusader period, making it no older than 1,000 years.

The new results put the original construction of the tomb in the time of Constantine, Rome's first Christian emperor.

In October 2016, the tomb itself was opened for the first time in centuries when the shrine that encloses the tomb, known as the Edicule, underwent a significant restoration by a team from the National Technical University of Athens.

Then, several samples of mortar from different locations within the Edicule were taken for dating, and the results were recently provided to National Geographic by chief scientific supervisor Antonia Moropoulou, who directed the Edicule restoration project.

After Constantine's representatives arrived in Jerusalem in around 325 to locate the tomb, they were apparently pointed to a Roman temple built some 200 years earlier. The Roman temple was razed and excavations beneath it revealed a tomb that had been hewn from a limestone cave. The cave's top was sheared off to expose the interior of the tomb, and the Edicule was built around it.

One feature of the tomb is a long shelf, or 'burial bed' which, according to tradition, was where the body of Jesus Christ was laid out following the crucifixion. Such shelves, hewn from limestone caves, are a common feature in the tombs of wealthy 1st-century Jews from Jerusalem.

According to pilgrim accounts, the marble cladding that covers the 'burial bed' was probably present since the mid-1300s.

When the tomb was opened on the night of October 26, 2016, scientists found an older, broken marble slab incised with a cross, resting directly on top of the original limestone surface of the 'burial bed'.

Now, the new test results reveal the lower slab was probably mortared in place in the mid-fourth century under the orders of Emperor Constantine.

'Obviously that date is spot-on for whatever Constantine did,' said the archaeologist Martin Biddle, who published a seminal study on the history of the tomb in 1999. 'That's very remarkable.'