Extraordinary cloud formations over two cities in China appear to have created an apparition of a floating city.

Footage of the phenomenon appears to show towerblock-like formations over the city of Foshan in the Guandong province of China, apparently bringing many people to a standstill in the street. It reportedly lasted only a few minutes before disappearing,

Experts said the phenomenon, a video of which was shown on Chinese television, was a common optical mirage, according to The Inquisitr.

Some internet users claimed the footage was evidence of "Project Blue Beam technology", based on a conspiracy theory that Nasa will at some point attempt to simulate the second coming of Christ or an alien invasion.

Online commentator Julie Wagoner said: "In my opinion, CERN , HAARP and Project Blue Beam could all have a little something to do with this. We just never know because the media only tells what the "elite" allow to be told. I am certain there are those of you who know what and who I am referring to when I say ,"elite". This is definitely something we will be seeing more of."

Another commentator, Goe Bann, said: "Interesting. What if it really is a city from a parallel universe? Or maybe a glimpse into the future."

But such outlandish suggestions were dismissed by experts, who say the visages are a trick of the eye, resulting from warm and cold weather bending light so that objects appear higher and larger than they really are.

Doubt was also cast on the validity of the video, which was the only apparent source available, with others claiming it had been Photoshopped. It was shown on some Chinese television, however.

One such mirage phenomenon is called a Fata Morgana, where the image of an object or objects is distorted from its original appearance as to be almost unrecognisable. It occurs because rays of light are bent when they pass through air layers of different temperatures.

The first film on a cloud, meanwhile, called a zoopraxiscope, was projected into the skies above Nottingham in the UK in a collaboration of artists and scientists called Project Nimbus. It depicted a green horseman galloping across the clouds, reported science blog Geek.