Star Warsfans have just been staggered to learn how the Death Star was actually constructed. A master manipulator, Palpatine tricked the Republic itself into beginning work on the Death Star - because they believed the Separatists were already building one.Work was already well underway before the Republic became the Empire.
But just how was such a massive battle-station constructed in secrecy? We know that a lot of the infrastructure was built at Geonosis, and it’s generally believed it was built in orbit. Surprisingly, though, De Agostini’sStar Wars Encyclopediasuggests a different method…

The Death Star Was Actually Built INSIDE A Planet
Cobalt Greenspotted this remarkable image on Twitter, and was staggered to share it; the image showsthe Death Star superstructure built inside a planet.This is an idea with roots in the oldStar WarsExpanded Universe, but it was thought to have been wiped from canon. It’s unclear which planet is shown here.
Naturally, this raises a lot of questions about just how such a feat of engineering would be possible. That’s especially true giventhe Republic would have had to complete a literally planet-sized construction facility during the Clone Wars, since the plans for the Death Star were only retrieved duringStar Wars: Episode II - Attack of the Clones.

The Death Star’s Construction Really Does Set Up Starkiller Base
This idea may seem rather absurd, but it does have two major advantages. The first is that this perhaps explains one of the strangest questions of the original trilogy; how was thesecond Death Starbuilt so quickly? This would perhaps make more sense if the Empire had essentially created a planet-sized conveyor belt system for when the prototype was finished.
The second is that this helps establish the strange links between the Death Star and Starkiller Base, an entire planet transformed into a superweapon byStar Wars: The Force Awakens. This “conveyor belt” system becomes the prototype for feats of engineering on a planetary scale.
Technically, De Agostini’sStar Wars Encyclopediais canon.It’s worth noting, though, that elements of Legends did tend to slip into these publications; some of them have been removed from later editions.Darth Plagueis' Sith Master, Darth Tenebrous, was named in one issue ofBuild the Millennium Falcon, but he was subsequently wiped.
So the Death Star’s surprising origin isStar Warscanon for now, but that may change.