Most complicated thingy

[AceofSpades]

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This is on the border of qualifying/not-qualifying because it creates electricity, but doesn't use it (or maybe I'm totally wrong, it was the first thing that came to my head, I really xon't know anything about the subject). The hydro-electric dam, it puts out a great deal of eletrical energy from the natural kinetic energy of the waters running through it. It's truly an amazing structure in both construction and use.

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I wouldn't say it's really that complex though, although quite amazing. My vote is for that mirror thingy.