I think that the most revolutionary of transformation in terms of the building arts, would have to be the introduction of steel. Steel allows an advantage to height challenges and gives an array of ways in which we interpret our existence on a global level.

We have, since the beginning of time, felt the need to build up to achieve a relationship with the cosmos. With the introduction of steel (and of course the advent of an elevator system), we have surpassed the limitations of our ancestors multiple times over. This is revolutionary because we are reaching heights that before, were never thought possible.

Skyscrapers also define landmarks in a urbanized location fat with economic growth and wealth. This communicates to the rest of the world a symbolic representation of the city that becomes the stamp in which it can be portrayed. An indication of a first world. Other building types and monuments can achieve this, but it is the grandeur of towers and skyscrapers, that achieve the awe and permanency in our minds.