The positions of the doorways relatively to the altars or the centres of the arcs is of interest; and we find that every important doorway in walls of the original period, with the exception of the south-eastern doorway in the temple at the Lundi, and the south-western one in the partly circular interior temple at Zimbabwe, is placed true north of the centre of an arc or of an altar, and the centre of every arc has had a doorway or some other means of marking out the meridian placed north of it. True north of the centre of the tower itself we have a doorway in the wall of the sacred enclosure, and although the wall in which this doorway is made was probably not built at the original period, yet there probably was a doorway in a similar position in the wall which it has replaced. The part of the great outer wall north of the tower seems also to have been marked, for about this point we found a great step constructed on its top about five feet high. Above the temple at the east end of the fortress on the hill, a cliff rises perpendicularly for fifty feet, and poised on its top there stands a most remarkable great rock which may once have been an object of veneration to the worshippers in the temple beneath it. It forms one of the highest points on the hill. A line drawn true south from this rock and produced 680 yards would pass through the doorway in the great temple and fall on the altar in the centre of the decorated arc. Until this line suggested itself we were puzzled to account for the peculiar character of the doorway. It passes through a wall sixteen feet thick, and is itself only three feet wide, and it does not pass through the wall at right angles, but cuts it somewhat obliquely, so that its axis is roughly parallel to the meridian line.