The plans of all the Assyrian buildings are rectangular, and we know that long ago, as now, the Eastern architects used this outline almost invariably, and upon it reared some of the most lovely and varied forms ever devised. They gather over the angles by graceful curves, and on the basis of an ordinary square hall carry up a minaret or a dome, an octagon or a circle. That this was sometimes done in Assyria is shown by the sculptures. Slabs from Kouyunjik show domes of varied form, and tower-like structures, each rising from a square base. The resemblance between the ancient form of the dome and those still used in the Assyrian villages is very striking. Whether sloping roofs were used is uncertain. Mr. Bonomi believes that they were, and a few sculptures seem to support his view. Of the private houses nothing, of course, remains; but they are represented on the slabs as being of several stories in height, the ground floor as usual having only a door and no windows. All have flat roofs, and we gather from one of the bas-reliefs, which represents a town on fire, that these roofs were made, just as they now are, with thick layers of earth on strong beams. These roofs are well-nigh fireproof, and the flames are represented as stopped by them, and coming out of the windows. No remains of a window, or, so far as we are aware, of an internal staircase, have been found.