Rogue One: A Star Wars Story brought Darth Vader back to the big screen, and gave us a glimpse of his home on Mustafar. While we didn't get to spend a huge amount of time exploring the Sith Lord's castle, we did briefly see Anakin Skywalker inside a bacta tank - likely his only refuge from the pain inflicted upon him while wearing the armour Emperor Palpatine created.
Now, thanks to concept artist Christian Alzmann, we have a closer look at the bacta tank and, in this earlier design, we get to see a much grander take on Darth Vader's only refuge. There's also an exterior shot of the castle, and we can only hope a future movie takes us back here.
After all, it was a major missed opportunity that the Star Wars sequels never followed Kylo Ren back to his grandfather's home on Mustafar, and it's hard to imagine why this was introduced if not to at least set the stage for a future story. It's hard to say whether Lucasfilm plans that far ahead, though, especially if the past few years of storytelling are anything to go by.
Check out this Rogue One: A Star Wars Story concept art below: