A growing skyscraper sheds its skin:
Because skyscrapers are lined with hard cement or brick rather than flexible mammalian skin, they need to shed their skin as they grow. The outer layer of any given skyscraper will slough off five to fifteen times over the course of the skyscrapers lifetime. In glass skyscrapers, the skin shatters and rains down on passersby, which is why you see them covered in special tarps during their construction.
Most skyscrapers over 40 stories will shed only during their development, ceasing to grow new skin once mature. Smaller buildings between 10 and 40 stories may continue to shed into adulthood, changing color or texture to match the whim of their owner.
The tower seen above is 44 stories and under development. Before it’s mature, this tower will also grow windows and if male, a lightning rod. A complete skyscraper of the same design can be seen in the background, it has shed for the last time and has its windows intact, making it at least 2 years old. It lacks a lightning rod and is thus a female skyscraper. This is the only known difference between skysexes.
Finally, note the ominous cloud. It’s not really important but boy is it ominous.