04-02-2018, 05:00 PM
I think it's an optical illusion. The vertical edges are all straight and parallel (or at least very close to it). The fact that the vertical edges don't really converge is one reason the top of the tower appears larger - our brains expects it to be smaller. This is also compounded by the fact that the balconies at the top come all the way to the corner of the building, effectively enhancing that flared effect.