I visited an aluminium smelter once. The main supply busbar was sitting at waist height and you could walk right up to it and place your hand on it while it was live....amazing. It was something like 2ft x 2ft in cross-section. Oh, and we had to take our watches off before we entered the potlines, otherwise they'd never work again after the internal mechanisms got magnetised. I was also told they could only drive diesel vehicles into the potline hall as the engines for petrol vehicles would stop because the coil would saturate and wouldn't reliably create a spark...something like that.
The other interesting thing was the elimination of metal loops in certain areas....all the handrails had non-conductive breaks in them, etc.