I saw an extremely ancient, antique electrical vault while performing obsolete equipment removal in Chicago. It was located in a 115 year old building. All copper busbars, switches, breakers, and other conductors, were completely un-insulated. You had to walk your way between them in a very particular way, to avoid an embarrassing death. I actually worked inside that vault to perform certain operations. It was a very educational experience. Everything was mounted on huge slabs of slate stone.