Scene as a worldmap? Picture in picture / Scene in scene

Problem introduction

Let's say, we got a game with 50 scenes onto which we transform players using the Application.LoadLevel() thing. Let's say Players can choose level using a static gui. However we have a 3D scene, which has nice and cute player-clickable islands. If we load up this scene, the player can choose an island by clicking on it, then it gets loaded using LoadLevel().

Now let's say, that a player is already ingame at an island scene. The player wants to open the 3D map in a small window without his current game terminating. Basicly we want picture in picture.

Question

How can we load a scene in a way, that it would not terminate the already loaded one, while the new scene appears as a gui-element (like a GUI.Window or GUI.Box or something) in a new 'gui-window'.

Application.LoadLevelAdditive and Application.LoadLevelAdditiveAsync allows you to load a level without exiting the currently one.

To render to a small window, you would need to use RenderTexture, which is a Unity3D Pro feature. You render that part of the scene which shows the 3d islands to a texture, then use that texture in a Unity GUI window. However, it will be tricky to determine which island the player has selected within that small window.