This integration is subtle. There are no giant turtle mountains here, but the same system we used for the giant turtle is applied here to produce the natural rock pillars that are connected by the bridges, also the platform where the pyramid rests:
These natural structures are defined by a low resolution mesh that captures the basic shape. This is expanded in realtime into detailed features like rocks, sand and dirt using procedural materials that we call Meta-materials.
The large terrain around the pillars and the pyramid's base is using Voxel Farm's standard procedural terrain.
This scene also uses UV-mapped voxels. This is a different method to apply textures to voxels. It allows much finer control. The entire pyramid is using them:
There is also the new instancing system, which is responsible for all the trees plants and rocks you see scattered around. You cannot see this in just screenshots, but this new system is able to preserve existing instances even in the event of user edits and destruction. This avoid the visible "replanting" of vegetation and rocks around edits.
And all this is running in Unreal Engine 4. I would say the UE4 integration is the last of the systems than went into taking these shots.