When Elon Musk and J.B. Straubel revealed the Gigafactory last year, I was struck with how they viewed it. According to Elon, the Gigafactory is itself a Tesla product, designed to be duplicated many times over. The entire factory is designed in CAD so that the location of every tube, conduit, and passageway can be optimized for the highest yield. When fully operational, the Gigafactory will produce more lithium batteries than the entire world produced in 2015. And they don't just make batteries there - the factory will also be used to manufacture Model 3 motors and gearboxes.
The gigafactory unveiling shows Tesla's thinking behind the Gigafactory. I highly recommend this.
This video shows the gigafactory from the outside, giving you a sense for the scale of the thing.
This video shows the inside of a Tesla Factory (I'm assuming the old NUMMI plant in Fremont)