A photo posted on the online forum Reddit is causing more than a few people to scratch their heads.

The picture, posted to the site by the Redditor zibin, shows construction workers repairing a bridge.

The angle of the photo makes it look like a real-life M.C. Escher drawing.

At first glance, it appears impossible for the workers to be at two different heights - looking at the elevation of the pillar and the position of the workers apparently atop the lift.

"The illusion is that the cherry picker is almost in the same orientation as if it were retracted, so it looks like the cherry picker is on the ground, with the workers investigating a very short bridge on their right," one user explains.

Interest in the picture has pushed it to the top of Reddit's front page, with many wondering how the optical illusion works.

A helpful illustration was provided by the user MrDLTE3.

The angle of the photo masks the cherry picker arm, which extends under the bridge diagonally, making the workers look closer to the ground than they really are.

The illusion if quick to decipher once you realise the arm of the cherry picker is being hidden.

Beyond the obvious illusion, some Reddit users have also noticed how one of the orange cones appears to float above the head of the third construction worker on the ground.

 

Source: New Zealand Herald