and that it lies at the bottom of the story of the 60 miles of circuit of Nineveh. The same circuit is given by Herodotus for the city of Babylon (cf. Chap. xv.). Of the third chief city, Asshur, which stood in ancient times, as we have seen, not only before Chalah, but also before Nineveh, nothing is left but heaps of refuse, out of which rises a conical hill. The ruins are of brick, among which here and there are seen some stones. The line of the old walls can still be traced. This city also formed a square, not less, but rather longer, in circuit than Chalah.[409] It seems that the kings of Assyria laid less weight on the fortification of the city of Asshur, than on the strengthening of Chalah and Nineveh. They saw danger in the west only, from the lower Euphrates. The city of Asshur, on the western bank of the Tigris, was exposed to attacks from the west; Chalah and Nineveh were covered in this direction by the Tigris, which the enemy had to cross. To make the two cities so covered impregnable from the eastern side also was the object of the kings of Assyria, especially of Sargon, Sennacherib, and Assurbanipal. The thickness given to the walls of Nineveh, Khorsabad, and Chalah (25 to 50 feet), was sufficient to defy the battering-ram--the turrets, raised to the elevation of 120 to 150 feet, were so high that the stones of the slingers and the arrows of the bowmen could not reach them with effect, and no scaling-ladder or besieging-tower could be set up which would carry men to these turrets.