Good one djrelc, something they will have trouble wriggling out of. Just one small point, its probably easier to say the towers are "perfectly vertical" rather than "perfectly level". If they are perfectly vertical (easy to measure with surveying tools or even a very long plumb line) and the distance between towers at water level is different to the distance between the towers at the top then this can join the many other proofs of a RE.
Of course, the same will be true for any other large bridge anywhere in the world.