For decades it was reported that an image of the City of Bristol, England, appeared in the skies of Alaska at a certain location. Various fake images were produced for Rickards, Phenomena A Book Of Wonders and though referred to over the years the actual photograph was said to be "lost" or "never existed".
This is what you read and hear when so called "experts" do not do any original research but crib from others -in this case the not always reliable Charles Fort. After over 100 years I found the image in question.
But over the years we have not seen anything similar....until now! Yes, thanks to technology we have an actual case -and footage- of a "city in the sky".
This from I F****** Love Science: http://www.iflscience.com/environment/what-caused-china-s-floating-city-sky