The walls which crown the flanking heights are of singularly massive construction, and defended by a deep wide moat cut out of the solid rock. As at Diarbekr and Urfa (and in Spain at Lugo and Astorga) they are strengthened at frequent intervals by solid projecting round towers.
Within the city itself are some even more notable monuments. The builders of the fortress did not rely exclusively on the river for their water-supply, but provided a huge underground cistern, fed by a rock-hewn conduit and capable of storing nearly five million gallons at need. This cistern consists of ten parallel vaulted tunnels, each about 150 feet long and 13 to 14 feet wide, with an internal height of 40 feet from the floor to the crown of the vault. The division walls of this structure are thickly encrusted with lime deposit, thus proving conclusively the purpose for which it was designed.
A little distance away is a sort of square platform of masonry, rising a few feet above the general level of the ground. We penetrated into it by a dark and narrow passage, and groping our way gingerly down a steep descent by the light of a couple of candles we found ourselves at last in a titanic cellar, 60 feet long and 50 wide, divided by a massive arcade into two naves, and roofed by a double barrel vault 50 feet above the level of the floor. This is doubtless the Great Granary mentioned by Zachariah of Mitylene; but (being underground) it is of course now deemed to have been a dungeon, and is known locally as "the Big Oubliette." The prodigious size of the stones employed in building it, and the extreme solidity of the masonry, made us think of the famous cisterns at Constantinople as very inferior structures indeed.[33]
The use of such very large stones is a notable feature of Dara and gives a more grandiose character to ruins magnificent in themselves. Two average sized blocks on the ramparts, which still lay conveniently _in situ_, afforded ample area for the accommodation of a camp bed; and each of the two taken separately must have weighed not much short of a ton. Even the houses appear to have been built of stones as large as those used in the fortifications. It would seem that they were employed in sheer bravado, as was undoubtedly the case with the yet bigger stones of Baalbec. Now all lie scattered at random over the whole area of the city, and it puzzles us not a little to conceive how such singularly solid buildings can have been so utterly overthrown. Earthquakes or battering rams might have demolished them; but then one would expect to find the débris lying in heaps as it fell. The stones might have been removed to construct new houses and enclosures; but then they would be disposed in some sort of regular lines. Did some Timour deliberately give order that no stone should be left upon another? Even he might have been daunted at such an undertaking, when the removal of each several block could employ a file of men for a day.