In a word: Persistence. Partly the traditional, inspiring, one man against all odds type of persistence, but more the obsessive, borderline insane persistence. But whatever, this dude's building his own metro, like a CITY, so I should probably shut up.
His name is Leonid Murlyanchik, and he is a mensch. (Is there a Russian word for that? Is mensch even considered German anymore? We should just start calling them "Murylanchiks" now anyway.) His story, based on what little I can glean from English Russia's sparse captioning, goes something like this: Leonid retired, and collected a healthy pension. He decided he needed a hobby, and apparently, better transportation. So he filed some papers, drew up some plans, bought some materials, and got going. He built his own concrete mixer, and began digging.
There's a lot more that we don't know, but makes for a fascinating Mad Lib: Why? (Fun!); Where does it go? (To a terror dungeon!); When will it be finished? (In time for the rest of the world to fall into unimaginable chaos and destruction!); What will the cars look like? (The heads of defunct Disney Characters!)
But in the absence of these facts, let us just enjoy another: There's an old man in Russia, digging out about 1 meter of soil a day, right now, for a personal subway system. Lots more photography at the source. [English Russia]