PARIS, FRANCE—The masonry of Notre Dame Cathedral is supported with 20-inch-long iron staples, according to a Live Science report. Construction of the cathedral began in the twelfth century and continued for 300 years. “This is the first building of its kind in which we see this,” said Maxime L’Héritier of Paris 8 University. L’Héritier and his colleagues carbon dated the iron staples, which held together the large arches in the nave of the structure, and in its twin towers, to around 1160. L’Héritier explained that the dates show the staples are the same age as the masonry, and were used during an initial phase of construction to form a supportive iron skeleton. “We believe that the staples were what enabled them to build this structure at such a terrific height,” L’Héritier said. He and his team are now analyzing the iron to try to determine if it was sourced locally or if it had been imported. So far, it appears that later staples may have been made from a different ore source. Read the original scholarly article about this research in PLOS ONE. To read about another discovery made during restoration of Notre Dame, go to "Around the World: France."