This mind-bending optical illusion is puzzling thousands on the Internet.

At first glance, the photograph appears to be of a regular brick wall:

Nothing exciting about that, you may think. But take another look.

Go on, really look. Do you see anything unusual? Nope? Don't worry, you're definitely not the only one to be perplexed.

Arron Bevin called the image one of the best optical illusions he'd seen when he posted it to Facebook on Monday.

Warning: the answer will be revealed further down.

Now look at it again -- and try to spot the cigar that's poking out from between two of the bricks. Aaaah, now you see it.

You're welcome!