Tips for hiding the scene edges from the player?

Hi!
I'm pretty new to unity in general, let alone to level building. The problem I encounter the most with 3D levels is that my player is often capable of seeing the end of the terrain.
In my game, the player is allowed to shoot an arrow to whichever direction he desires, and then the camera follows the arrow for a couple of seconds. So even if I raise a load of mountains or buildings around the edges, he can still shoot an arrow over them and see beyond the terrain.

I'm not asking what to do with my specific case of the arrow camera, but rather curious how do you guys usually solve this kind of problems, regarding the scene edges?

 

Natural barriers (walls, mountains, gorges, etc.), some set pieces beyond them, and then a skybox (that includes pre-rendered extended terrain) beyond that.