The outer bailey is the southernmost feature of the castle; it is pentagon shaped and there are five towers spaced along the wall, three of which are at corners. North of the outer bailey is the middle bailey which is an irregular polygon; like the outer bailey, the wall of the middle bailey is studded with towers. The towers allowed the garrison to provide enfilading fire. In the fashion of the time, most of the towers in the curtain walls of the middle and outer baileys were cylindrical. Château Gaillard was one of the first castles in Europe to use machicolations—stone projections on top of a wall with openings that allowed objects to be dropped on an enemy at the base of the wall. Machicolations were introduced to Western architecture as a result of the Crusades. Until the 13th century, the tops of towers in European castles had usually been surrounded by wooden galleries, which served the same purpose as machicolations. An Eastern innovation, they may have originated in the first half of the 8th century.