One thing I frequently do with my open world maps is splitting them up into chunks and containing them, this map is currently no different, the main draw for that is primarily an optimisation need, if I can split up environments in this way then I can keep them from loading and hit better performance marks.
It does however mean the map can break down into multiple chokepoints between regions, so I'm working to try and ease that pain through numerous potential connections, and keeping them relatively open.
alongside the train tunnels, there are a few other entry points to this section around the combine trainyard, a hidden away cabin, and a abandoned mineshaft. all of these will enable passage to the other regions on my creation list (Antlion town, rebel base, and combine base)
Rebel base explorations are ongoing, the cave entrance was seen before, and due to displacement limits being a more concious factor, I've switched some of the environment other to a bunker concept for now.
Although after so much C24 combat, I've decided the silo doors are not going to be interactable, they'll all remain open by default as static meshes.
One other exploration piece I'll likely rebuild, but a stolen power source with a trapped APC.