Here I present You my older work, before my existence on Artstation :).
The source of images are mixed but in general terrains were made with World Creator and Gaea. Sometimes exported them to Unity and Unreal. In Unity and Unreal I used various of assets, Enviro, Microsplat, Nature Manufacture foliage and trees assets and many more :). Textures are mostly Game Textures and Substance sources from old Allegorithmic :)