Drifting along at eight knots under a full moon atop a man-made mountain in a man-made river you feel that you have entered some fabled land of giant beasts and Homeric heroes. The ships as impossibly large, floating cities. The Centenario Bridge, which spans the narrowest portion of the Panama Canal, the Culebra Cut, hangs over the water like the trap of some prehistoric arachnid. The locks, which raise and lower the ships 27m across the 80km route, are at once incredibly simple in concept and inconceivably complex in function that they seem contrived by some powerful necromancer. It is all so monstrous and mythical. And yet it was ordinary men that built this Tower of Babel. A century ago, the lowly bipeds of a small isthmus nation unaided from above or below built something on the scale of nature's grandest treasures. It's baffling.