I am currently building a city level for a college project. We have a city block with buildings, surrounded by walls and I want the player to be able to see a city outside the walls without having to create all the added geometry. What is the best way to do this? I already have found some free use city panoramas that I could use. I just don’t know the best way to go about this. Thank you.
Either use very low poly meshes (like you can see in the shooter demo map) or just use a plane with your panorama texture (like in the sun temple → the cliffs) 
The best way is probably low poly buildings or buildings with LOD for the nearest buildings and then a panorama texture for the buildings further away.
This kit is built like that: Megacity Kit
What about using some like a cubemap? Is this the correct occasion to use one? Also, if I just break the panorama into 4 squares and put it on 4 planes around the level, would there be seems? would it appear warped from certain angles? Sorry I’m kind of new to unreal.
Instead of splitting it you could just bend the plane → then you wont see any seams + it looks more realistic. How it will look like depends on the distance between the actual level and those panorama planes. I havent tested cubemaps, but theoretically it should work ^^