On my last visit to the Buffalo Trace distillery in Kentucky, I took a very cool tour of the property that you can read about at that link.
On a visit this past February as part of the Bourbon Classic event in Louisville, I had another tour that was completely different and I learned all new stuff. I never mind going to distilleries multiple times as there is always something new to pick up.
Below are just some miscellaneous facts I picked up, rather than the whole picture.
As it has been operating since 1787, Buffalo Trace is the oldest continually operating distillery in the US. They have 100 buildings on a property that stretches 130 acres, with 320,000 barrels aging on-site.
Buffalo Trace makes 17 bourbons at the distillery (plus a few other products), distilling five days a week. Despite this, they use just one strain of yeast for all their products.
In the fermentation process, 2/3 of the mash is 'sweet mash' that has just been fermented, while the remaining third is 'sour mash' that comes as the waste solids of the first distillation.
They use four water sources: spring water, reservoir water, river water, and municipal water. The first waters are filtered through sand and used in fermentation. The river water is also used in cooling after distillation (I'm guessing unfiltered). The municipal water is reverse-osmosis filtered to bring spirits down to bottle strength, as is the norm.
There's always more to learn on future visits...