there's not many relics that are anything like this size. there's a little window here where you can actually touch the wood itself. unfortunately, we can't open up this reliquary and take this wood with us or subject it to any scientific sampling. however, what i'd really like to do is to get something like it into a proper laboratory environment where we can explore it further. >> to help him in his search, dr. kazan's starting point is a fascinating project by a 19th century french architect named charles rohault de fleury. he set out to add up all the pieces of the true cross. >> this map shows the places which he documented as having wood of the cross, and he worked out that all of this wood from all the places that he'd been to didn't come up to 10 percent of the total volume needed to put