To the west of the Southern Citadel, and therefore at the place where originally the Euphrates flowed, there is a remarkable building that strikes one by the immense thickness of its walls, 20 to 25 metres in width. It is not yet completely excavated. The upper part has been removed at no very distant period by modern brick robbers, and the many holes and mounds in the neighbourhood still bear witness to their nefarious handiwork. The wall throughout is of solid compact brickwork, built with excellent Nebuchadnezzar bricks laid in asphalt. Between this building and the moat wall of Imgur-Bel a narrow ditch is left; at its north and south ends only connecting pieces are jointed in, pierced by several holes to allow the water to pass. The western limits are not yet clearly definable. The somewhat long quadrilateral of the ground-plan was divided by cross walls into a number of separate divisions, of which the southernmost remained open, while the others were occupied by a number of dwelling-like chambers. A great stairway or ascending ramp is recognisable in the north-east corner of the southern open space. During the building the ground plan was subjected in various places to slight alterations. The Nabonidus wall, which stretches from the south, joins on to the south-west corner of the building with a tower, and the canal that flows from the east passes through this tower. It is evident that this building is the place referred to in Nebuchadnezzar’s Sippar cylinder (_K.B._ iii. 2, p. 49, col. 2 l. 19): “In order that no harm (?) should happen to the stronghold of Esagila and Babylon, I caused a great fortification to be built in the river (ḫa-al-zi ra-bi-tim i-na nâri) of bitumen and bricks. I raised its foundation on the depths of the water, its top I exalted like the wooded mountains” (trans. by Winckler). XXIV THE THREE GREAT FORTIFICATION WALLS NORTH OF THE SOUTHERN CITADEL We now turn our attention to the three fortification walls, that follow the direction of the ancient Arachtu walls, but which overlap them and stretch farther to the west.