The following contains spoilers for Rogue One: A Star Wars Story . Read at your own risk.
The newest entry in the Star Wars franchise introduced many new things to the canon. However, one of the most interesting is what it added to the backstory of a well-known character, Darth Vader. The new film shows us a massive castle-like structure which appears to be Vader's home when he's not flying across the galaxy. Surprisingly, even with so much of the Star Wars extended universe being declared non-canon, there's still a lot about the building that we know.
The reference was to the planet Mustafar, where the empire took Jedi after The Clone Wars in order to torture them and get information. Mustafar is also the location of the climactic battle between Anakin Skywalker and Obi-Wan Kenobi that leaves the former Jedi crippled at the end of Star Wars: The Revenge of the Sith. It's a more than curious decision that Darth Vader would place his palace in the middle of the planet that nearly destroyed him, but there we can see some of Anakin's conflicted nature.
In addition, it turns out that the location of Darth Vader's home was very nearly a part of Star Wars: The Return of the Jedi. Concept art was created that would have showed the location years ago, though it didn't end up being used.
Also, according to the companion art book to Rogue One: A Star Wars Story, the structure is built on top of some sort of Sith cave. The book doesn't go into too much detail but this would appear to be an odd detail to include if it's not important. There has been some discussion that the building could appear in future Star Wars movies, possibly as early as Star Wars: Episode VIII so maybe the cave will be important to whatever quest Luke is on in the primary saga.
Finally, when we first see Darth Vader he is emerging from a large tank. This is a Bacta Tank, similar to the one that Luke Skywalker is put into after being rescued at the beginning of Star Wars: The Empire Strikes Back. The art book for Rogue One says that this is the only place that Vader feels comfortable, which would explain why the location is so prominent in his home.
Do you think we'll see Darth Vader's castle down the line? Let us know your theories in the comments below.