In general, you have two ways:
1. You generate terrains in Unity Editor, modify it as you need, and use this pre-generated terrains in the application.
2. Terrain (mesh) generates runtime.
In the first case, you can modify terrain and textures, add some objects, and completely control the result.
But if you want to go to Bergen, you can not do it.
You will need to open the project and generate this city.
In the second case, your application will be smaller, and if you want you can go to Bergen or even New York.
But you can not (almost) affect the result, which will generate Online Maps.
Kind Regards,
Infinity Code Team.
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