How that crazy city of Knowhere in Guardians of the Galaxy was made

One of the reasons I enjoyed Guardians of the Galaxy so much was because I got to explore a world in which I had no expectations. Take that crazy city Knowhere, which is inside a giant Celestial head, I didn't even know it existed, let alone know what it "should" look like. Here's the VFX reel showing how the city was built.
Read more: https://gizmodo.com/how-that-crazy-city-of-knowhere-in-guardians-of-the-gal-1692510696?source=Snapzu