For anyone in Europe I can recommend a visit to Völklingen Hütte (https://en.wikipedia.org/wiki/V%C3%B6lklingen_Ironworks). I went there last year on holiday in Germany.
It's an old iron factory built into a museum. Most parts are open to public and are left in a 'frozen' state since it was closed in '86 (although maintained and sometimes still fully functional). It's a really nice travel in time and insight into an industry of this scale. I remember how parts of the complex seen organised and architected and other parts are just a big mess of pipes and parts that have been added and shoved in over the decades that this factory ran (24/7, all season, without a roof, I might add).