Stare at the dot as the colors get imprinted on your eyes. When the animated .gif flips over, you'll see the building in color. It's not in color. :)
From here. Another version of this is here, where you mouse over the pic to change it after staring. That page also has a tutorial on how to make your own.
Hm, let me see....
Click on the small pic to load the full-size gif and start the animation. Then stare at the black dot until the picture changes. :)
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