Ecbatana was chiefly celebrated for the magnificence of its palace, a structure ascribed by Diodorus to Semiramis, but most probably constructed originally by Cyaxares, and improved, enlarged, and embellished by the Achaemenian monarchs. According to the judicious and moderate Polybius, who prefaces his account by a protest against exaggeration and over-coloring, the circumference of the building was seven stades, or 1420 yards, somewhat more than four fifths of an English mile. This size, which a little exceeds that of the palace mound at Susa, while it is in its turn a little exceeded by the palatial platform at Persepolis, may well be accepted as probably close to the truth. Judging, however, from the analogy of the above-mentioned palaces, we must conclude that the area thus assigned to the royal residence was far from being entirely covered with buildings. One half of the space, perhaps more, would be occupied by large open courts, paved probably with marble, surrounding the various blocks of buildings and separating them from one another. The buildings themselves may be conjectured to have resembled those of the Achaemenian monarchs at Susa and Persepolis, with the exception, apparently, that the pillars, which formed their most striking characteristic, were for the most part of wood rather than o£ stone. Polybius distinguishes the pillars into two classes, those of the main buildings, and those which skirted the courts, from which it would appear that at Ecbatana the courts were surrounded by colonnades, as they were commonly in Greek and Roman houses. These wooden pillars, all either of cedar or of cypress, supported beams of a similar material, which crossed each other at right angles, leaving square spaces between, which were then filled in with woodwork. Above the whole a roof was placed, sloping at an angle, and composed (as we are told) of silver plates in the shape of tiles. The pillars, beams, and the rest of the woodwork were likewise coated with thin laminse of the precious metals, even gold being used for this purpose to a certain extent.