One of the most impressive synthesizer studios in the world must be Cevin Keys Subconscious studios in LA. Not least because Key has managed to produce quite a bit of impressive music there as well, especially the Download and Plateau releases. Here Phil Western, Keys long time musical collaborator, gives a tour of the facilities in 2010:
And here's a clip showing studio work taking place at Subconscious in the summer of 2012:
The following clip shows a much earlier incarnation of Subconscious studios in January of 1995, before it was relocated from Vancouver to LA. The clips feature among others Skinny Puppy and Download member Dwayne R. Goettel, who sadly passed away from a heroin overdose six months later. This clip is probably from the sessions that resulted in Downloads first album "Furnace".
I know I've seen another clip of Cevin Key giving a tour of the studio but can't seem to find it on Youtube at least. If you'r unfamiliar with Keys music and want to try out some of his stuff I would recommend that you start with Download's "Helicopter" and/or Plateau's "Gort Spacebar".