A hiker found himself in an “unbelievable” situation when he found himself mesmerized by an extremely rare weather phenomenon known as a “mountain specter” or Brocken specter during his walk through North Wales.

Truck driver Liam Roberts of Bangor was climbing local mountain Moel Eilio when he witnessed the strange site, reports The Independent.The illusion appears when the sun is low in the sky and the observer who is standing in front of the sun is on very high ground while looking down on clouds, mist, or fog, according to BBC. The result is a halo-like image where the person’s shadow is crowned by a circular “glory.

The halo is often rainbow colored, hence the name glory, and the 35-year-old was able to take some brilliant photos of the phenomenon.

“I’ve never seen anything like this before… I’m speechless,” Roberts told PA news agency.

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“I kind of turned around to look at the views and I see this circle. I honestly thought it was some kind of rainbow it kept getting brighter then it disappeared then came back for about four minutes.

“It was unbelievable I couldn’t take my eyes off it, it was so unreal I was shocked.”

The term Brocken specter was coined in 1780 by German pastor and scientist Johann Silberschlag, an avid hiker of the Harz mountains in northern Germany.

The term has been mentioned in the literary works of Samuel Taylor Coleridge, Charles Dickens, Lewis Carroll, and others.