Linear Game Terrain (Dark Souls Style)

Does anyone know how exactly to go about making landscapes and terrain like that of Dark Souls, the new God of War, and games in the similar collection with a generally linear path? I know a lot of content creators usually just sculpt the terrain from the landscape tools but as far as those games, the landscape really just consists of a model of a landscape with surrounding low poly models to fill in the background, but how do you create that landscape style?