Soviet train tunnels in mountains to avoid going uphill? That's interesting. European Russia is mostly flat. And a list of the world's longest tunnels has many in China, but only a handful dating from the days of the Soviet Union, and those are the metro lines of Moscow, St. Petersburg, Minsk, Kharkiv and Kiev. Admittedly those works are very grand. But they weren't built through mountains, or "just to avoid having to go uphill." Could Professor James please provide a source for his narrative on this point?

https://en.wikipedia.org/wiki/List_of_longest_tunnels.