I've begun looking into 3D game development and I want to create something with an open world. The problem that I anticipate having is that backdrop landscaping such as mountains and city skylines will get really straining performance-wise since the open-world implies you can actually visit them (plus, as a designer I don't like putting up invisible walls everywhere to break the immersion.)
A solution I've been able to come up with is creating a high- medium- and low-detail version of pieces of landscape and render them in a particular fashion depending on how far away the player is.
However, are there any better ways to take care of this problem? I wouldn't exactly like to have three of each resource (if not more) in order to make my game run smoothly.