the rule than the exception; and, in the palaces, “Throne-rooms” are commonly mere deep recesses of this character, vaulted or supported by pillars, and open at one end to the full width and height of the apartment.  The height of the arch varies in Sassanian 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 twenty-five to forty 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 seventy 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.  A series of semi-circular arches is thrown across the angles of the apartment, each projecting further into it than the preceding, and in this way the corners are got rid of, and the square converted into the circular shape.  A cornice ran round the apartment, either above or below the pendentives, or sometimes both above and below.  The domes were pierced by a number of small holes, which admitted some light, and the upper part of the walls between the pendentives was also pierced by windows.

There are no passages or corridors in the Sassanian palaces.  The rooms for the most part open one into the other.  Where this is not the case, they give upon a common meeting-ground, which is either an open court, or a large vaulted apartment.  The openings are in general doorways of moderate size, but sometimes they are arches of the full width of the subordinate room or apartment.  As many as seventeen or eighteen rooms have been found in a palace.

There is no appearance in any Sassanian edifice of a real second story.  The famous Takht-i-Khosru presents externally the semblance of such an arrangement; but this seems to have been a mere feature of the external ornamentation, and to have had nothing to do with the interior.

The exterior ornamentation of the Sassanian buildings was by pilasters, by arched recesses, by cornices, and sometimes by string-courses.  An ornamentation at once simple and elegant is that of the lateral faces of the palace at Firuzabad, where long reed-like pilasters are carried from the ground to the cornice, while between them are a series of tall narrow doubly recessed arches.  Far less satisfactory is the much more elaborate design adopted at Ctesiphon, where six series of blind arches of different kinds are superimposed the one on the other, with string-courses between them, and with pilasters, placed singly or in pairs, separating the arches into groups, and not regularly superimposed, as pillars, whether real or seeming, ought to be.