It is difficult to suppose that the real city--the streets and squares--can at any time have occupied one half of this enormous area, A clear space, we are told, was left for a considerable distance inside the wall--like the _pomaerium_ of the Romans--upon which no houses were allowed to be built. When houses began, they were far from being continuous; gardens, orchards, even fields, were interspersed among the buildings; and it was supposed that the inhabitants, when besieged, could grow sufficient corn for their own consumption within the walls. Still the whole area was laid out with straight streets, or perhaps one should say with roads (for the houses cannot have been continuous along them), which cut one another everywhere at right angles, like the streets of some German towns. The wall of the town was pierced with a hundred gates, twenty-five (we may suppose) in each face, and the roads led straight to these portals, the whole area being thus cut up into square blocks. The houses were in general lofty, being three or even four stories high. They are said to have had vaulted roofs, which were not protected externally with any tiling, since the climate was so dry as to render such a protection unnecessary. The beams used in the houses were of palm-wood, all other timber being scarce in the country; and such pillars as the houses could boast were of the same material. The construction of these last was very rude. Around posts of palm-wood were twisted wisps of rushes, which were covered with plaster, and then colored according the taste of the owner. The Euphrates ran through the town, dividing it nearly in half. Its banks were lined throughout with quays of brick laid in bitumen, and were further guarded by two walls of brick, which skirted them along their whole length. In each of these walls were twenty-five gates, corresponding to the number of the streets which gave upon the river; and outside each gate was a sloped landing place, by which you could descend to the water’s edge, if you had occasion to cross the river. Boats were kept ready at these landing-places to convey passengers from side to side; while for those who disliked this method of conveyance a bridge was provided of a somewhat peculiar construction. A number of stone piers were erected in the bed of the stream, firmly clamped together with fastenings of iron and lead; wooden drawbridges connected pier with pier during the day, and on these passengers passed over; but at night they were withdrawn, in order that the bridge might not be used during the dark. Diodorus declares that besides this bridge, to which he assigns a length of five stades (about 1000 yards) and a breadth of 30 feet, the two sides of the river were joined together by a tunnel, which was fifteen feet wide and twelve high to the spring of its arched roof.