Love Lock Bridge : Hohenzollern Bridge
For reasons largely unknown in about 2008 people began attaching love locks to the bridge, and when there ceased to be room for more locks, to other preexisting locks. The resulting patchwork of iron and steel forms a dense wall almost impenetrable by light, years of rusting have caused many of the locks to become permanently fused to one another.
There is a long and somewhat mythical history surrounding the love locks and their appearance around the world. In keeping with the astounding ability of Asia to generate absurd and awesome folklore they have some of my favorite explanations, including magnetic wish granting fields generated by passing trains. Greece, not to be outdone in the field of crazy folklore answers right back with the story of Nada and Relja.
Of all the many things to see in Cologne the love lock bridge stands out as the most honest and important, primarily due to it not being intended to draw in tourists.