In 1970, Henry Lincoln came upon the enigma that surrounds the small village of Rennes-le-Chateau, set in the foothills of the Pyrenees. "The Holy Place" is a natural and perfect pentacle of mountain peaks surrounded by a titanic, man-made temple. The author had to decode the most cryptic of clues that have dispersed down the centuries in paintings and parchments, on tombstones and in churches. It has now been revealed as an immense geometric temple, stretching for miles across the landscape, a constellation of pentacles, circles and hexagons. The complexity of its engineering far exceeds that of the pyramids of Egypt and led the author to question just how it could have been built. Using evidence in measure-mapping and surveying, the author demonstrates that the basic measurements for this amazing structure has a precise mathematical basis and is not the result of arbitrary calculations. Henry Lincoln is the co-author of "The Holy Blood and the Holy Grail" and is the presentor of BBC TV's "Chronicle" programmes.