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This isn't a gadget—and it's even a couple of years old—but we think you'll forgive this weekend foray into "Oh, wow!" engineering. This bit of concrete and steel is the Falkirk Wheel, a boat lift connecting two canals near Falkirk, Scotland.

Thanks to Archimedes' principle (floating objects displace their own weight), each water-filled caisson weighs the same amount. That allows the entire counter-balanced tip to bring boats—water and all—up or down to the next canal using just a 1.5 kilowatt-hours of energy—the same amount of energy it takes to boil eight kettles of water.


'Rotating lock' lifts boats, links waterways [DesignNews]

Falkirk Wheel [Wikipedia]