What is the largest Terrain Size allowed in a Scene and maximum number of Scenes in a Game?

I tried making a scene larger than 2000x2000 and it seems to have been truncated to that. Is that the largest possible size of a terrain in a scene?

And can there only be one terrain in a scene? Or could I butt them against each other?

Also how many scenes can I have in a game?

Look at the bootcamp demo and load up the one with Unity 3.1 While they don't provide all the scenes and terrain in the project file, you can start to see how they situate smaller terrains within a larger world.

Also, see the neighbor functions on Terrain

http://unity3d.com/support/documentation/ScriptReference/Terrain.SetNeighbors.html

Yes, it is possible... Currently I use a matrix of 3x3 terrains 3200x3200 world unit wide each. I generated my heightmaps with World Machine, then used SetNeighbors to get rid of the LOD problem in their seams, changed the far plane so I can see all that with my cam, and everything is working fine, I can move in them perfectly.

I don't know if there's an actual limit of how big your terrain can be except by resolution and memory consumption. It is best to keep your terrains smaller and page them somehow, or cull them, than having a huge terrain.

The limit is 1 million in length and width

Seprate questions... But do you need big of a terrain? You should model it and import it from the program if you really need that.

And you can have more than one, problem is you can see the gaps if the player is near the ground... And someone made a program helper, I believe is called stitchscape to help with this... But yeah.

As to scenes, I'd believe unlimited haha.

You can make it whatever size you like, but the bigger it is, the lower the resolution. You can increase the heightmap resolution up to 2049x2049. You can make however many terrains and scenes as you like (practically speaking).