A "floating city" seen in the skies above China has shocked residents.
The film shows what appear to be skyscrapers within the clouds above a city in the country.
Video footage has triggered onlookers to speculate the "city" is home to alien life or perhaps even a parallel universe.
Another reportedly suggested it was a hologram produced by authorities.
Skyscrapers look like they're hanging in the clouds
This - dubbed Project Blue Beam Test - is said to involve NASA simulating an alien invasion of earth.
The sight has been spotted four times over the past two years, the Daily Express reports.
And it is due to a weather phenomenon known as "fata morgana" - the so-called optical distortion and inversion of distant objects with the images becoming stacked.
A similar illusion can occur with boats.
It is due to a weather phenomenon
According the Express, Suryanarayana Maddu told an online forum: "Our brain assumes that light travels in a straight paths, so when it bends, we think the object is where it would be if the light's path runs straight.
"In this case, light reflected from the skyscrapers is bent downward as it passes through the colder, denser air.
"Because the brain puts the object where it would be if the light traveled a straight path, the distant skyscrapers appear higher than they actually are."