been happening -- what had happened in the past was that you had a lot of pilgrims that were eager to take a little piece of the tomb away with them. so custodians of the church eventually covered the original rock with marble slaps to prevent souvenir gatherers, so to speak. >> so the experts believe the marble was placed more than 400 years ago, in 1555? well, yes, this is -- that's one historical account we have. it may have been been placed even earlier, by the 1370s. what we are finding, when the scientific team is finding in working together is that we have multiple layers of marble going down, marble slabs and we need to work with all of those in order to expose the rock and seal it. what is happening the shrine that encompasses the tomb, the