These old steam locomotives might not be environmentally friendly but they're amazing to watch and listen to. I've heard the big boy is great to see in person if you get the chance (they've talked about doing a tour of the west coast of the US for a few years now, hopefully it will happen next year).

If you're into this kind of stuff, check out this video of Union Pacific's 3985 pulling a 143 car intermodal train all by herself back in 1990: https://youtu.be/XhgHrDbN4EU

Of course these heavy hauls are hard on the engine, even just the equivalent of replacing brake pads costs tens of thousands of dollars.