This class is an in-depth study of tall buildings and the concept of efficiency. The methodology of the class will follow two parallel trajectories. The first trajectory is the study of efficiency, a widely used concept, albeit often, without a precise definition as to what it really means. In architectural discourse, the use of efficiency oscillates between loosely-defined anecdotal claims of Ôbuildings being highly efficientÕ and the short-sighted analytical approach of simple ratios, usually reported in a single percentage like usable-to-gross floor area.