During the 11th and 12th centuries, the number of imposing masonry keeps apparently did not increase significantly, probably because of the huge cost. The model remained very much as previously described: a rectangular donjon of a height between 20 and 30 m, the entrance placed on the first level, three or four stories, few openings, a shirt, and so on. But toward the end of the 12th century, important changes took place in the castle plans, giving rise to a process of evolution and development. These changes were due largely to the experience gained in the Crusades by western military engineers, who for the first time had made a close acquaintance with Middle East culture and the mighty fortifications of the Byzantine empire. The most significant of these changes was the general discarding of the rectangular masonry keep in favor of a circular outline. The progress of Romanesque religious architecture had brought about the domination of cylindrical volume and round form in churches (in the apse, the apsidal chapel, and the chancel). These technical improvements influenced military construction, and many works built in this period present
Cross-section and ground-plan of the Tour Blanche in Issoudun. Built on a 16 m high motte between 1187 and 1195, the Issoudun donjon (Indre, France) gives a good example of 12th century rounded form.
World History
