Each building has its own uniqueness and eye catching design. The architects and building designers are the mastermind behind this uniqueness in each building's design.
Everyone has their way to express themselves through design and the use of material. A building is like an art work and each decade has its own use of space and material. For example, in the 1960s and 1970s the buildings were mostly about concrete, whereas, in the 2000s it's all about having more windows, energy efficiency, and sustainability.