"With such an array of indispensable structures carrying so many waters, compare, if you will, the idle Pyramids or the useless, though famous, works of the Greeks!"
Frontinus, The Aqueducts of Rome (I.16)
The aqueduct on the outskirt of Tarragona is a magnificent structure, made all the more so by its isolated setting. The uppermost of the two tiers extends more than seven hundred feet, as can be better appreciated from this perspective. 
Reference: Frontinus: Stratagems, Aqueducts (1925) translated by Charles E. Bennett and Mary B. McElwain (Loeb Classical Library).
