The halls and chambers were grouped around two great courts measuring about 350 by 200 feet. The hareem formed a separate set of buildings, as did also the stables and outhouses. The walls were of great thickness, evidently for coolness. They were decorated with slabs of alabaster, enamelled tiles, and designs painted on stucco. There has been much speculation on the method of roofing these rooms, some believing that circular vaults were employed and others that wooden beams, supported on wooden columns, similar to the stone ones found in Persian palaces, were used for this purpose. The latter theory seems the more probable, as the local manner of building is the same as this at the present day. No traces of columns remain, however, and the spans are in many cases too great to be roofed by single pieces of timber. One of the most interesting discoveries made at Khorsabad was the gate of the city, the jambs supporting a semicircular arch over a span of eighteen feet. The gate was a double one having two separate passages, one for vehicles and the other for pedestrians: the marks of chariot-wheels still remaining in the pavement of the former. The sides were ornamented with winged bulls, and the archivolts of the arches were decorated with blue and yellow designs in enamelled tiles. It had been long supposed that the Etruscans were the first to make use of the true semicircular arch (_i.e._, formed of wedge-shaped stones or bricks, with joints radiating to a common centre), but this discovery, and the finding of pointed arches in the sewers of Babylon, by Layard, places the date when both these expedients were known, at a much remoter period, though even these are probably much later than the examples found in Egypt. No complete example of a Chaldean temple has been found, but there are several the lower stories of which are sufficiently well preserved to give an accurate idea of their size and details, and in the tomb of Cyrus at Passagardæ, in Persia, we have probably a model on a small scale of one of these buildings when entire. This tomb consists of a platform of six steps, eighteen feet high, surmounted by a rectangular chamber. The latter has a doorway and a ridged roof abutting against pediments. It has been surmised that all the temples were like this, consisting of a chamber or cella built on the summit of a several-storied structure, each story being either concentric and reached by a ramp winding around the four sides or placed farther to one side than that immediately below it and approached by straight flights of stairs.