liebana. it's home to the largest and most revered piece of helena's discovery. dr. georges kazan is an archaeologist here to investigate the mystery of the true cross. >> what's at stake here is the truth about the origins of this relic. is it something that dates back from the time of christ? >> this relic is said to have been brought in the 5th century from jerusalem by a monk called toribio, and this relic is enormous by the standards of relics of the cross.