Detail this asset from Unity Asset Store: Original Link
This is a paid asset, but now you can download PolyWorld: Woodland Low Poly Toolkit Free.
PolyWorld: Woodland Low Poly Toolkit v2.4 (Latest version)
Polyworld: Woodland Toolkit is the defacto standard suite of tools and 3D artwork to create a flat-shaded, lowpoly world inside Unity.
Add Interiors with Polyworld: Low Poly Fantasy Interiors!
Terrain Generation has been completely rewritten!
-Create your world using the familiar Unity Terrain tools and heightfields, paint infinite terrain textures, then convert that to a low poly, Polyworld terrain.
-Convert any mesh, even characters, to the PolyWorld style. Any 3d object in the asset store can be used! *blendshapes not supported yet
-Includes a vast array of prefabs and meshes in the same low poly art style.
-14 faceted skyboxes with associated ambient cubemaps give you a variety of lighting conditions.
-Powerful mesh combine script to reduce draw calls for mobile
-Desktop and Mobile demo scenes!
-Compatible with Gaia,Fantasy Treasure Loot Kit and TaD – Sewer Kit
There will be imitators, but no other pack in the store offers what PolyWorld can do.