How to make a high quality cubemap

Hey guys, i am getting a little frustrated with cubemaps. I’ve been trying to make a Skybox with only one image (cubemap) but no matter how the image is, i always end up having the same result: A bad quality skybox. I am talking of something like downloading an 100x100 image and then extending it up to 2000x2000 pixels, this is the quality i am getting.

The part that i didn’t get was why does this happen. Are cubemaps like this normally or am i missing some standard resolution requirement? Seriously, i’ve tried using images up to 6.000x6.000 pixels full hd and 4k, images that you can zoom in as much as you like and it will still be HD.

What do you have the resolution set to in the Cubemap settings? I think it defaults to 128, and it will scale down any images that you add to that resolution. Once you change the resolution, you need to reimport the images into the cubemap for it to recognize them.