In Star Wars: The Force Awakens, we see that the First Order has constructed a massive superweapon called the Starkiller, very similar to the two previous Death Stars, though much more powerful, and much, MUCH larger, as observed when the members of the Resistance are comparing it in size to the original Death Star.
In addition, the Starkiller is built into the planet it's on!!!
The first question that comes to mind is how the First Order even accomplished this amazing feat. But the real question is:
How did the First Order build Starkiller base so quickly?
Since The Force Awakens happens just about 30 years after The Return of the Jedi, when there is no hint of the Starkiller even existing, and considering that the original, much smaller Death Star took over twenty years to construct, how is this even possible?