I've been following the Atlantic City Boardwalk organ restoration for a couple of years. It's a really incredible instrument and they have done some amazing work.
One of my favorite recordings is Cliffton Stround's rendition of Abide with Me.
It was done in the 90s before a lot of the restoration work had taken place. At the time, I think only 25-30% of the instrument was functioning. He starts with the quietest stops on the organ and gradually add stops as he goes. This gradual crescendo hits a point towards the end where you don't think it can get any bigger but it keeps growing! To think that such a small percentage of the instrument was functioning and it gets as loud and powerful as it does is truly mind blowing. I can't even imagine the raw power the instrument will have when it is fully functional.
This is a really fascinating video done last year giving a bit of history and tour of the instrument.