You'll now find train entrances scattered across the world, typically you'll find entrances next to existing monuments. Upon the first inspection, they may not appear to be anything special but after venturing inside deep below the terrain, you'll now find a vast rail network with drivable workcarts.
When entering the train entrances you'll notice the huge spiral staircases penetrating deep into the terrain, central to the stairs you'll find a much quicker, but perhaps less safe elevator shaft.
Everything in Rust wants you dead, these tunnels are no exception. Upon reaching the bottom of the shafts you'll encounter some not so friendly tunnel dwellers. From this point forward you'll likely encounter many more dwellers if you decide to continue exploring.
With risk comes reward, while the dwellers may be unwelcoming the loot they protect could well worth the risk.
After exploring the shafts and tunnels you'll finally be standing at the rail platform. On each platform, you'll encounter more dwellers but increasingly better loot.
At the end of each platform, you'll find a driveable workcart.
Consider this a first pass of a new dungeon system. Everything here is procedurally generated and we plan to add new track segments, bespoke entrances at each monument, puzzles, new NPCs, and eventually use this system to procedurally generate the cave network.