My other hobby was, for many years, railroad. Both scale and full size.
Presently there is much excitement on the upcoming 150th anniversary celebration of the completion of the transcontinental railroad at Prometory Utah. The Union Pacific has spent several million dollars and tens of thousands of man hours restoring to service one of the surviving examples of their famous Big Boy locomotives, which were considered to be the largest steam locomotives ever built. At 133' long and 1.25 million pounds, they were indeed huge.
Most later steam power was built on a one piece cast frame. In this, which could be 90' long, the entire cylinders, everything from frontvto back, was literally cast as a single piece. I doubt a foundry exists today that would try it.
In the pic, only a couple bars bolted below the 4 openings for the journal boxes for the main drive axels are not part of this casting. Other than these small pieces, this entire thing is cast as a single piece.