How to create big open world like skyrim or bigger

from what i’ve learned so far,you can use a Heigh maps as suggested by A GUPTA. Once you have your picture, you can import it direclty in unreal by going in the landscape tool. Try different setings, apply a base material to it. You will surely want toknow more about Vertex painting once done. Havent test it myself, but it looks pretty useful and easy to use!

Good luck