Was it Fata Morgana, an optical illusion, which caused a floating city to be seen in the skies of China? But looking at the video clip hopefully viewable above, you can see that the floating city was unlike any city known. Fata Morgana is a type of mirage, which distorts the object or objects which they are based on significantly, often such that the object is completely unrecognizable.  So maybe it was that an entire city somewhere got its image distorted and Fata Morgana carried that off into the sky.
It is Arthurian, in a way. Fata Morgana is named for the sorceress Morgan le Fay. The earliest accounts of Geoffrey of Monmouth in Vita Merlini refer to Morgan le Fay in conjunction with the Isle of Apples (Avalon) to which the fatally wounded King Arthur was carried off. 
Or was the strange floating city seen in China really a Project Blue Beam experiment? Serge Monast, a Québécois investigative journalist, poet, essayist and conspiracy theorist, published in 1994 the book, Project Blue Beam (NASA). Monast claimed that NASA, with the help of the United Nations, was attempting to implement a New Age religion with the Antichrist at its head and start a New World Order, via a technologically simulated Second Coming of Christ. 
We have now the last of a tetrad of Blood Moons having occurred at the end of September 2015; the “tipping point” New Moon of October 13 (00:06 UTC) 2015 ; the armies of the world gathering in Syria, in the vicinity of Har-Megiddo (Armageddon); and now possibly the “New Jerusalem” seen in the skies of China.
“And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband.” (Revelation 21: 2)
Today some would tell John of Patmos, “Oh tut tut. It was a Fata Morgana.” How comforting it is for some to dispel anxiety via magical terms from the so-called science! Yet there are more things in heaven and earth, Horatio, than are dreamt of in your philosophy. 
“Onlookers”, reports Britain’s Express newspaper, “were said to be mesmerised as a towering city of sky scrapers appeared from the clouds.”  The “heavenly formation”, reports Australia’s 9News, “appeared in two separate incidents, first early last week in the city of Foshan, and a few days later in the province of Jiangxi.” 
End Times or Project Blue Beam? The NASA Blue Beam Project has four steps, the first two being: (1) the breakdown of all archeological knowledge (as occurred in Iraq and now in Syria); (2) a gigantic “space show” with three-dimensional optical holograms and sounds (test of project possibly done now in China). 
Strange things seen in the skies were the life’s work of Charles Fort (1874 – 1932). In several books Fort meticulously catalogued anomalies. Were there “new lands”? Considered was that there are “Lands in the sky – That they are nearby – That they do not move.” Indications that there is a “shell” surrounding our existence. 
- June 1801: A mirage of an unknown city. “It was seen, for more than an hour, at Youghal, Co. Cork, Ireland – a representation of mansions…” 
- October 28, 1812: Phantom soldiers seen at Havarah Park, near Ripley, England. Scientists explained it all away as “mirages of troops marching somewhere at a distance.” 
- September 7, 1820: “Things that marched in the sky” seen concurrent with an eclipse. The marching things moved “in straight lines, turning and retracting in the same straight lines, all of them separated by uniform spaces.” 
- September 27, 1846: In Liverpool, a city was seen in the sky. Called a “mirage”, it occurred coincident to a panorama of Edinburgh being on display in Liverpool. 
- July 1878: In Parkersburg, West Virginia, an “opaque substance” which looked like “a white horse, ‘swimming in the clear atmosphere'” was seen. Explained away as a mirage. 
- Circa 1881: White-robed figures seen in the sky. Armed uniformed soldiers seen to be drilling in the sky. Platoons of angels seen to be “marching and counter-marching in the sky, their white robes and helmets gleaming.” Also seen in the sky: “the figure of President Garfield, who had died not long before.” 
- April 1897: Letters to editors of several newspapers tell of “airships” seen. A “mysterious light” seen in the sky of Kansas City, “something like a powerful searchlight.” The “searchlight” was traveling east at about 60 miles-per-hour. A week later, an airship was seen above Chicago. Reports from other towns in Texas: “It was shaped like a Mexican cigar, large in the middle, and small at both ends, with great wings, resembling those of an enormous butterfly. It was brilliantly illuminated by the rays of two great searchlights…” In Chicago, the sky object was photographed. It looked like “‘a cigar-shaped, silken bag,’ with a framework…” In Carlensville, Illinois “the airship had alighted upon a farm, but had sailed away when approached – ‘cigar-shaped, with wings, and a canopy on top.'” 
——- Sources ——-
 “Fata Morgana (mirage)”, Wikipedia, October 18, 2015.
 “Morgan le Fay”, Wikipedia, October 18, 2015.
 “Serge Monast”, Wikipedia, October 18, 2015. https://en.wikipedia.org/wiki/Serge_Monast
 “Strange Things Are Happening”, Ersjdamoo’s Blog, October 13, 2015. https://ersjdamoo.wordpress.com/2015/10/13/strange-things-are-happening/
 Hamlet, by “William Shakespeare” (Francis Bacon et al.). http://www.shakespeare-online.com/quickquotes/quickquotehamletdreamt.html
 “Did parallel universe open up? Hundreds see ‘floating city’ filmed in skies above China”, by Jon Austin. Express (UK, online), October 17, 2015. http://tinyurl.com/qdkl8po
 “Cloud ‘floating city’ sparks conspiracy debate”, 9News Australia, October 18, 2015. http://tinyurl.com/p5ylvz4
 “Project Blue Beam”, The Watcher Files. http://www.thewatcherfiles.com/bluebeam.html
 The Complete Books of Charles Fort. New York: Dover Publications, 1974.
 New Lands. From The Complete Books of Charles Fort, op. cit.