you could import a real world location instead of making your own terrain. theres tutorials on doing this on yotuube and its not limited. you can probably do an entire continent if you want to and if u got some NASA computer. i followed the one called “Importing real world location to UE4” and I ended up with capetown south africa. its 8X8km. you could do that for free with that editor you could only get a trial version of.