n. Unusable space at the top of a tall building created by a spire or similar extension added only to give the building extra height.
Dubai's Burj Khalifa — currently the world's tallest building at 2,717 feet — is topped by 800 feet of unusable ornamentation. That means almost 30 percent of the world's tallest building is "vanity height."
Some of the world’s tallest skyscrapers have been criticised for being built with added "vanity height", which serves no practical purpose other than to push them into the architectural category of "supertall".
Tall buildings can be economical when it comes to saving space, high land prices and creating density, but at some point, the height of a building doesn’t have a rational meaning any more, but an emotional one. One could argue that the difference between a tall building and a skyscraper is vanity height.