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

BBC: Venice removes Charles Ray Boy with Frog statue

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