Making an environment that looks good is a time-consuming hard task without proper tools. My intention with this article is to show you a bunch of very good asset that will help you a lot to make your world in Unity.
Recently encountered with Struffel Production on Patreon. He is creating PBR materials. The best part is that you can download these for free from his website. There are an insane amount of PBR mats: 170+ and its growing.
Dark Fantasy Kit is a modular 3D PBR environment package which contains 400+ prefabs to create a residence of a villain or evil mastermind of your RPG game with a First Person, Third Person or a Top-Down view. Works with Unity versions from 5.6 to 2018.