I was wondering why the Empire chose to build the second Death Star in orbit around the Forest Moon of Endor?
I guess that having locals who aren't capable of space flight is handy, but aren't there fully uninhabited planets hidden away in the Outer Rim, that would be just as defensible, and less well-known to the rest of the galaxy?
Apparently Endor is known for producing Ewok Jerky, so you'd imagine that many people would want more, take a trip, and notice the Death Star being built there.
Simply put, the Endor system was simultaneously incredibly remote (dramatically lowering the chances of anyone stumbling onto the project by accident) and highly accessible if you knew the secret navigational codes that were required to access the "Sanctuary Pipeline", a lengthy hyperspace route that led directly from Sullust to Endor.
Red lines appeared on the spiral arms—the great trade routes that connected the galaxy’s star systems. Ackbar gestured, and a red dot sprang into existence in a location Leia recognized: Sullust, the homeworld of Nien Nunb. Then another dot appeared, on the edge of the galaxy. A dotted blue line stretched between them.
“The Empire has used S-thread boosters to create and maintain a secret hyperspace route running from Sullust all the way to the galactic edge,” Ackbar said. “It’s called the Sanctuary Pipeline and is one of the Empire’s most important military secrets. Fortunately, our agents discovered the navigational data that will allow us to use it, too.”
As to why Endor was chosen (over, say, another more accessible but still unexplored planet), that was down to the Emperor himself.
The shield generator could have been built in any of thousands of desolate, lifeless planetary systems. But the Emperor himself picked this spot from several suggested by Imperial engineers.
The engineers liked the idea of burning up the moon’s resources to fuel the shield.
And the Emperor liked the idea of crushing something beautiful.
In addition to Valourm's answer, The Emperor also knew about the Rebel fleet massing near Sullust. Remember that the entire thing was a trap, and he was creating the best, most irresistible bait for it he that he could. Including the possibility of killing both him AND Vader, in a single stroke. The shuttle and the codes being stolen were all part of his scheme to crush the Rebellion in one, swift stroke.
