With the population in this temper it would have been futile to inquire into the prospects of constitutional government. I spent a day among ancient churches;[202] and a day upon the walls, which are as fine an example of mediæval fortification as any that exists. They hang, upon the south and south-east sides, high over the Tigris--it was from this direction that Sapor’s troops effected an entry through a hollow passage that led down to the water’s edge. On the south-west they crown a slope set thick with gardens of mulberry and vine, and towards the north the wall bends round to join the curve of the river. Four great gateways break this circuit. The Mardîn Gate commands the terraced gardens, and the road that passes through it runs down to an ancient bridge over the Tigris (Fig. 206). To the north-west and north the Aleppo or Mountain Gate and the Kharpût Gate open on to a fertile plain, and the Yeni Kapu, the New Gate, stands above the precipitous southern bank (Fig. 207).[203] The lie of the ground makes it certain that the oldest fortifications of the city must have occupied much the same position as those which still surround it, and though the latter are proved by numerous inscriptions to be Mohammadan work of different periods, I should judge them to be built mainly upon ancient foundations. The north wall with its round towers is perfectly preserved; even the domed chambers inside the towers, together with the stairs that gave access to the _chemin de ronde_, are intact. All the arches and domes in the interior of the towers are of brick. Between the Kharpût and the Aleppo Gates a small aqueduct brings water to the town, the few springs within the walls being unpleasantly brackish. The citadel commands the north-east angle above the river; most of the space surrounded by its enclosing wall is occupied by modern buildings and by a mound whereon stood the castle of the first Mohammadan princes. The domed arsenal is said to have been a Christian church, but remembering my unsuccessful attempts to visit the arsenal at Baghdâd, I did not ask permission to enter it.[204] From a postern gate in the north wall a road leads down to the river, passing under a cliff out of which gushes a sulphurous spring. As I watched the soldiers of the garrison washing their clothes in its waters, I tried to reconcile it with “the rich spring, drinkable, indeed, but often tainted with hot vapours,” which Ammianus Marcellinus describes as rising under the citadel, and to see the men of the 5th Parthian Legion in the ragged groups standing about it.[205] From the citadel we walked to the Mardîn Gate along the _chemin de ronde_, a fine course, lifted high above the close air of the city and swept by the breezes that come down from Taurus (Fig. 208). Between the Aleppo Gate and the Mardîn Gate stand two huge round towers, larger than any others and later in date.[206] Near the Mardîn Gate the _chemin de ronde_ is