 The surface level is almost horizontal: the roadway lies at a height of 20.05 – 20.55 m (65.8 – 67.4 ft) above sea level between arches 1 to 20, and falls slightly in its eastern section, between arches 21 and 26 to a level of 19.94 to 19.66 m (65.4 to 64.5 ft). Since there is no indication of a later sinking of the structure, this nearly uniform height indicates careful levelling and the existence of solid pier foundations. In contrast, the lengthwise axis of the bridge displays often significant deviations from arch to arch.
