I'm so glad someone else mentioned JERUSALEM, easily one of the most detailed and lived-in sets I've ever seen. Nothing too complicated, just dense with rich specificity and thoroughly engrossing.
Also, the reveal of the full set in SEMINAR was indeed a special moment. Similar to that, though, for me, I have to say the first set that came to mind was the first revival of GLENGARRY GLEN ROSS. When the Act II curtain up and those fluorescent lights flickered on to the ransacked office set, it was breathtaking. Coming from the flat lip-of-the-stage Chinese Restaurant, the reveal of the massive depth and incredibly-detailed office (complete with sidewalk and street down the block from the office's front entrance so actors could be seen approaching the office) was stunning. It got applause the day I saw it.
Words don't deserve that kind of malarkey. They're innocent, neutral, precise, standing for this, describing that, meaning the other, so if you look after them you can build bridges across incomprehension and chaos. But when they get their corners knocked off, they're no good anymore…I don't think writers are sacred, but words are. They deserve respect. If you get the right ones in the right order, you can nudge the world a little.