Thirteen of these are still standing, and the position of all the others is well defined by broken bases or shafts. They are of two different kinds, the one having a capital composed of double-headed bulls, and the other a capital with volutes, not placed horizontally as we see them in classical columns, but vertically and resting on a complicated series of mouldings. These last may have been also surmounted by the double-headed bulls, as without such an addition the columns are shorter than the others, which measure 67 feet 4 inches. The beams which they sustained, rested upon the body of the bull between the two heads. The shafts of the columns at Persepolis are fluted and taper upward from the bases, which are elaborately ornamented with mouldings. It is probable that the Greek Ionic capital was derived directly from the Persian voluted model, as the order originated in the Greek colony in Asia Minor. The Chehil Minar is the finest building on the platform, the other halls of Darius and Xerxes being smaller, and though a hall containing 100 columns has been found, it is inferior in height, the total altitude not exceeding twenty-five feet. The hall of Darius contained sixteen columns, forming a square, preceded by a portico with eight more. The walls have long since disappeared, but the façade of the building is reproduced upon the face of the rock-cut tomb of Darius in the neighbouring hill called Naksh-i-Rustam, so that a restoration of the structure as it originally appeared is easily made. This tomb shows the four front columns of the porch with double-headed capitals, sustaining an entablature, above this is placed an attic decorated with bass-reliefs and a figure is represented standing on the top in the act of sacrificing on an altar. The stone buildings of Persia are generally supposed to be reproductions of the wooden constructions of Assyria, as the character of the art is similar in both, the bass-reliefs and winged bulls of Persepolis being practically identical with those of Nineveh. We find no traces of Assyrian art for several centuries after the erection of the buildings just described, though it is probable that it had influence in all Eastern edifices erected during the interval, not only in Asia, but in Greece and later in Byzance. There was evidently a revival of Assyrian taste during the dynasty of Sassanian kings who reigned between the third and seventh centuries of our era. The remnants of their palaces are found at Firouzabad, Al Hadhr, Serbistan, Ctesiphon, and Mashita, where we find large halls vaulted and domed and ornamented in a manner directly traceable to the ancient buildings in Assyria. The chief peculiarity of these structures lies in the use of the horseshoe or elliptical arch, which is found nowhere else. The porch of the Tak-Kesra at Ctesiphon consists of a great elliptical tunnel-vault, 115 feet deep, 85 feet high, over a span of 72 feet.