Mysterious Floating City Appears In China

A mysterious city emerges in the skies over China. Some say it is a different dimension or aliens, while others say it is a mirage. This isn't the first time this is happened either. It has happened dating back to 2011 and every year since 2015 with the exception of last year. Can something happen multiple times and still be a mirage? Will it happen this year?

The last time this happened was on January 14th, 2017 over Yueyang in Hunan province in South Central China.
According to experts, the skyline of this hallucination, do not match any known city in the world. So this squashes the theory about the pollution clearing up and the citizens seeing the city's skyline for the first time as some hypothesized.

Is this an example of some new type of holographic projection technology similar to the long-rumored but never confirmed Project Blue Beam?

Some Experts say that this is an illusion brought on by radiation fog. 

If i lived there i'd probably rather believe it was aliens than radiation fog playing with my mind.

What do you believe?