How do I copy a terrain?

This question was answered CORRECTLY by @Bunny83 here: http://answers.unity3d.com/questions/25335/duplicate-terrain.html#answer-1155927

1. Duplicate your Terrain asset (IN YOUR ASSETS FILES).

2. Duplicate your Terrain object (IN THE HIERARCHY).

3. Open the Debug window into the inspector of the duplicated terrain object. --- INTO DEBUG WINDOW ---

4. Terrain -> Terrain data = change to your duplicated terrain asset.

5. Terrain Collider -> Terrain data = change to your duplicated terrain asset.

The best way to do this is to make a prefab of your Terrain 1, then instantiate it when necessary, using the instantiate command.

Let's say you name your terrain "Terrain1". In a script, declare a variable "terrain", then instantiate it using Unity's Instantiate function.

 public GameObject terrain
 
 //changeSeason is a placeholder. It's just to show when you want to change seasons
 if (changeSeason) {
     Instantiate (terrain, new Vector3(0.0f, 0.0f, 0.0f), Quaternion.identity);
 }

Quaternion.identity is for default rotation (0, 0, 0), and new Vector3() is to create new coordinates for where it starts in global space.

Changes made to copies of terrain will effect all copies created from the same terrain data, to have unique terrain assets you will need to create a whole new terrain (you can copy height maps for the same shape and allow it to be changeable if using separate terrain data)

How I would approach this is I would:

1) Sculpt terrain the way I want it. (Assuming the terrain doesn't change)

2) Decorate the terrain appropriately.

3) Copy/save the splat map (I have never done this)

4) Create a new gameobject and make all decorations children of it.

5) Select the gameobject and save it a prefab for that season, each game day have the script Instantiate the prefab (at the same position you had the gameobject when you made your decorations children of it so everything lines up with the terrain) then change the terrains splat map to whatever season you want. (the splat texture is data for the painted textures on the terrain)