Here you can find several cliff high quality models and example how to gather landscape using this models.
Triangles count:
Huge stone 1 - 6000 tris
Huge stone 2 - 4990 tris
Big stone - 5000 tris
Flat stone 1 - 2000 tris
Flat stone 2 - 5830 tris
Flat stone 3 - 3990 tris
Mid stone 1 - 4000 tris
Mid stone 2 - 960 tris
Small stones (for all 5 meshes) - 7018 tris
Technical Details
Texture Sizes: 2048x2048
Collision: no
Vertex Count: 18000
LODs: no
Number of Meshes: 16
Number of Materials and Material Instances: 7
Number of Textures: 23
Supported Development Platforms: Win, Mac
Supported Target Build Platforms: Win, Mac