C'mon! Someone spent that much time stitching?? For what purpose?
Not someone,
something. It's done with computer software and little human interaction. Camera sensors have only so much physical "real estate", so in essence, this software creates an image only possible with a camera sensor a thousand times bigger than what is currently available. Google "gigapixel image" for examples of this technique used in art, science, etc.
https://en.wikipedia.org/wiki/Gigapixel_imageEDIT: They have one for Trump's inauguration, too: http://www.cnn.com/interactive/2017/01/politics/trump-inauguration-gigapixel/