Erebor

Erebor, the Lonely Mountain of the Dwarfs.

I created the mountain in Gaea and exported it as an 8K heightmap into Terragen, where I slightly changed its base form.
The other features of the terrain were created in Terragen, and I used four different tree types to populate the scene.
The ice blocks floating in the lake were quickly modeled in Blender and exported as Obj files to which a glass shader with subsurface scattering was applied in Terragen.