Rogue One will have to settle for being the second-highest grossing film of the year — damn you, cultural juggernaut Finding Dory! — but it does have the distinction of being among the better-reviewed films in its franchise. Many critics have praised director Gareth Edwards’ vision of some unexplored pockets of George Lucas’ universe, singling out Darth Vader’s castle lair that appears in the film on a violent, molten-lava planet. (The planet bears a strong resemblance to Mustafar, the magma-covered site of the final showdown between Anakin Skywalker and Obi-wan Kenobi in Revenge of the Sith.) Now, one of the key designers from Rogue One has provided a little background on the memorable locale and how it came to be.

Doug Chiang was one of the artists instrumental in imagining the world of Rogue One, and in a new interview for, he spoke about the carefully-considered design for Vader’s castle. Chiang explained:

In our minds, we started to come up with a little bit of a backstory. That perhaps this place had special meaning for [Vader], and that this is where he comes to meditate and to heal himself. We started with the idea that maybe it should be built around his bacta tank chamber, and he comes back here to rejuvenate himself and also to meditate. So from there, the structure itself grew out from the bacta tank, and there were certain ideas that we tried. We were trying to go for a very iconic shape, and we always love tall towers. Ralph McQuarrie actually drew quite a few small thumbnail sketches [of Vader’s castle] that were very intriguing. They were kind of angular versions of a tower, and I saw the potential of where he was going, and I just exaggerated that quite a bit.

The bacta tank, for those who have forgotten, is a cylindrical chamber where a body can be exposed to the fictitious chemical bacta, said to accelerate the healing process. Vader, stuck in a perpetual state of decay, needed it to stay alive. It’s a neat factoid, knowing that Chiang took that into consideration while designing the castle, but moreover, it’s indicative of the insane level of detail that goes into the Star Wars pictures. Every rock, tree, and post-industrial hallway has been carefully mapped out.