The method of spanning or roofing spaces by means of corbelling has recommended itself quite widely to primitive peoples. It has been recognized in a number of prehistoric cultures: the megalithic tombs of Copper Age Iberia, tombs such as Maes Howe, Orkney and Newgrange, Co. Meath, in the British Isles, as well as several tombs in Brittany, employ the method. The Sacred Wells of the Nuragic Culture in Sardinia were also roofed with corbelled domes. In these west European examples the gap spanned by corbelling tends to be relatively small, two or three metres, and the slope of the corbelling conservative. The point is demonstrated clearly by the ‘tholos tombs’ of Iberia; the greatest distance of their chambers is covered by a single slab, and their walls are corbelled out only a relatively short distance. The technique was by no means limited to the illiterate communities of prehistoric Europe. Relatively modern examples have been reported from the south of France and from Italy, where the technique is used for roofing buildings which are not covered by the earthen mounds found over the megalithic tombs. The Egyptians of the Old Kingdom used a steep and narrow corbelling to roof the passages and chambers of, for example, the Bent Pyramid of Sneferu, and the Great Pyramid of Kheops at Giza. However the skill and daring of the Mycenaean engineers who commonly spanned distances of eight metres, and in the largest tombs over fourteen, is unmatched in the history of the technique. Indeed only the invention of the true dome enabled larger spaces to be bridged without internal supports. As the Mycenaean tholos tombs illustrate the technique at its most perfect, they provide an especially appropriate example from which to examine the principles of corbelled structures.