Metro 2033; a reworking of Dmitry Glukhovsky's 2002 novel of the same name and a story that investigates a post-nuclear holocaust Moscow where survivors live in the city's expansive underground Metro system.
That's the premise behind the post-apocalyptic world you'll find yourself in. The story itself revolves around protagonist Artyom, a young adult who's grown up in this network of underground Metro stations, never before seeing the light of day. Of course, it wouldn't be much of a story if there wasn't a catalyst forcing Artyom away from his daily routine and, ultimately, out into the ruins of Moscow itself. This comes initially in the form of mutants that attack humans through the underground network, and then from a new threat to the survival of mankind.