The height of the arch varies in Sassanid buildings from about fifty to eighty−five feet; it is generally plain, and without ornament; but in one case we meet with a foiling of small arches round the great one, which has an effect that is not unpleasing. The domed apartments are squares of from 25 to 40 feet, or a little more. The domes are circular at their base, but a section of them would exhibit a half ellipse, with its longest and shortest diameters proportioned as three to two. The height to which they rise from the ground is not much above 70 feet. A single building will have two or three domes, either of the same size, or occasionally of different dimensions. It is a peculiarity of their construction that they rest not on drums, but on pendentives of a curious character.