Was googling, found some interesting numbers, this is usable space Boeing Everett Factory, Washington State - 13.38 million square meters Target import house, Savannah Georgia - 7.43 million square meters NASA vehicle assembly building, Florida - 32,374 square meters O2 Arena, London = 104,634 square metters Gigafactory, when completed - 13.6 million square meters. I'd hate to know what the air conditioning bill is of the Boeing factory. But even more impressive to know that the gigafactory will be powered by Solar Cells (Net Zero in fact). As a comparison, the other largest green building being built, the Apple spaceship campus, is a ring that is 472 meters in diameter. The gigafactory is a solid rectangle (almost) that is 1100 meters long. And the second largest building in the world currently, by floor space, is the Tesla factory in Fremont. Mind blowing!