The original photograph, made under cloudy skies, was fairly washed out. I added contrast and pumped up the vibrancy of the colors, and saturated the green a bit. The interesting bridges were enhanced, I think, by the lucky s-curve of the train tracks. I'm not sure why the s-curve is touted as a worthy addition to a photograph; I suppose it helps lead the eye to the main subject or, in this case, subjects.