South of Nineveh, at the distance of about twenty miles by the direct route and thirty by the course of the Tigris, stood the second city of the empire, Calah, the site of which is marked by the extensive ruins at Nimrud. [PLATE XXIV., Fig. 1.] Broadly, this place may be said to have been built at the confluence of the Tigris with the Upper Zab; but in strictness it was on the Tigris only, the Zab flowing five or six miles further to the south, and entering the Tigris at least nine miles below the Nimrud ruins. These ruins at present occupy an area somewhat short of a thousand English acres, which is little more than one-half of the area of the ruins of Nineveh; but it is thought that the place was in ancient times considerably larger, and that the united action of the Tigris and some winter streams has swept away no small portion of the ruins. They form at present an irregular quadrangle, the sides of which face the four cardinal points. On the north and east the rampart may still be distinctly traced. It was flanked with towers along its whole course, and pierced at uncertain intervals by gates, but was nowhere of very great strength or dimensions. On the south side it must have been especially weak, for there it has disappeared altogether. Here, however, it seems probable that the Tigris and the Shor Derreh stream, to which the present obliteration of the wall may be ascribed, formed in ancient times a sufficient protection. Towards the west, it seems to be certain that the Tigris (which is now a mile off) anciently flowed close to the city. On this side, directly facing the river, and extending along it a distance of 600 yards, or more than a third of a mile, was the royal quarter, or portion of the city occupied by the palaces of the kings. It consisted of a raised platform, forty feet above the level of the plain, composed in some parts of rubbish, in others of regular layers of sun-dried bricks, and cased on every side with solid stone masonry, containing an area of sixty English acres, and in shape almost a regular rectangle, 560 yards long, and from 350 to 450 broad. The platform was protected at its edges by a parapet, and is thought to have been ascended in various places by wide staircases, or inclined ways, leading up from the plain. The greater part of its area is occupied by the remains of palaces constructed by various native kings, of which a more particular account will be given in the chapter on the architecture and other arts of the Assyrians. It contains also the ruins of two small temples, and abuts at its north-western angle on the most singular structure which has as yet been discovered among the remains of the Assyrian cities. This is the famous tower or pyramid which looms so conspicuously over the Assyrian plams, and which has always attracted the special notice of the traveller. [PLATE XXIV., Fig. 2.] An exact description of this remarkable edifice will be given hereafter.