With a click, he flipped the image upside down, and the legs became long arms, like those on a monkey.

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"It's like a Surrealistic joke, to turn such an iconic structure upside down and bend its image, " said Mr. Recoder.

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On closer inspection, the machinery turns out to be a trompe-l'oeil painting and the interior a mirrored image of one built upside down behind the painting.

WSJ: Too Clever by Half | More Real? | Minneapolis Institute of Arts | By Peter Plagens

Some animal-lovers also argued that the image of a boy holding the frog upside down was cruel, our correspondent adds.

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