Flavius Josephus, The Wars of the Jews
William Whiston, A.M., Ed.

[136] THE city of Jerusalem was fortified with three walls, on such parts as were not encompassed with unpassable valleys; for in such places it had but one wall. The city was built upon two hills, which are opposite to one another, and have a valley to divide them asunder; at which valley the corresponding rows of houses on both hills end. Of these hills, that which contains the upper city is much higher, and in length more direct. Accordingly, it was called the "Citadel," by king David; he was the father of that Solomon who built this temple at the first; but it is by us called the "Upper Market-place." But the other hill, which was called "Acra," and sustains the lower city, is of the shape of a moon when she is horned; over against this there was a third hill, but naturally lower than Acra, and parted formerly from the other by a broad valley. However, in those times when the Asamoneans reigned, they filled up that valley with earth, and had a mind to join the city to the temple. They then took off part of the height of Acra, and reduced it to be of less elevation than it was before, that the temple might be superior to it. Now the Valley of the Cheesemongers, as it was called, and was that which we told you before distinguished the hill of the upper city from that of the lower, extended as far as Siloam; for that is the name of a fountain which hath sweet water in it, and this in great plenty also. But on the outsides, these hills are surrounded by deep valleys, and by reason of the precipices to them belonging on both sides they are every where unpassable.