WTC TT Lobby from inside, the walls, external and cores were stupendously massive and thick.

The WTC TT Lobby was a real sight to behold, equivalent to several stories in a normal building. the external and core walls were composed of massively thick columns and could most easily support the 109 stories above itself. The safety factor or collapse efficience, (Collapse Load/Live Load) = (CL/LL) was at least 110 and probably far more that 2,000, being that John Skilling declared that one tower could top load support more that 20 Twin Tower's gravitationally base weight.