The Roman History · Amm. 19.5.4

In a remote part of the walls on the southern side, which looks down on the Tigris, there was a high tower, below which yawned an abrupt precipice, which it was impossible to look over without giddiness. From this by a hollow subterranean passage along the foot of the mountain some steps were cut with great skill, which led up to the level of the city, by which water was secretly obtained from the river, as we have seen to be the case in all the fortresses in that district which are situated on any river.

Ammianus Marcellinus · translated by C. D. Yonge · 1911 reprint
C. D. Yonge translation (preface dated February 1862); G. Bell and Sons, 1911; Project Gutenberg #28587
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