Atypical image ahu (fig. 36) is composed of a long wall running parallel with the sea, which, in a large specimen, is as much as 15 feet in height and 300 feet in length; it is buttressed on the land side with a great slope of masonry. The wall is in three divisions. The main or central portion projects in the form of a terrace on which the images stood, with their backs to the sea; it is therefore broad enough to carry their oval bed-plates; these measure up to about 10 feet in length by 8 feet or 9 feet in width, and are flush with the top of the wall. On the great ahu of Tongariki there have been fifteen statues, but sometimes an ahu has carried one figure only. The wall which forms the landward side of the terrace is continued on either hand in a straight line, thus adding a wing at each end of the central portion which stands somewhat farther back from the sea (fig. 41). Images were sometimes placed on the wings, but it was not usual. From this continuous wall the masonry slopes steeply till it reaches a containing wall, some 3 feet high, formed of finely wrought slabs of great size and of peculiar shape; the workmanship put into this wall is usually the most highly finished of any part of the ahu. Extending inland from the foot of this low wall is a large, raised, and smoothly paved expanse. The upper surface of this, too, has an appreciable fall, or slope, inland, though it is almost horizontal, when compared with the glacis. By the method of construction of this area, vault accommodation is obtained between its surface pavement and the sheet of volcanic rock below, on which the whole rests. In the largest specimen the whole slope of masonry, measured that is from either the sea-wall of the wing or from the landward wall of the terrace to its farthest extent, is about 250 feet. Beyond this the ground is sometimes levelled for another 50 or 60 yards, forming a smooth sward which much enhanced the appearance of the ahu. In two cases the ahu is approached by a strip of narrow pavement formed of water-worn boulders laid flat, and bordered with the same kind of stone set on end; one of these pavements is 220 feet in length by 12 feet in width, the other is somewhat smaller (fig. 93). [Illustration: FIG. 36.—DIAGRAM OF IMAGE AHU. ]