system
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human
[MCU] Where would Celestials even stand?

Given the size of Knowhere, in Guardians of the Galaxy, the Celestial whose head it was must have been enormous.  How big were they, and where would they have lived?  
  
I mean, if your head is around the size of the moon, Earth wouldn’t be big enough for you, would it?
gpt
Because the Celestial we see in GoTG, Eson the Searcher, is essentially identical to its 616 counterpart, we can assume they share the same height of 2000 feet. This is the standard Celestial height (there are far taller ones like Exitar at 20,000 ft). The Celestial whose remains became Knowhere fits somewhere in this range but closer to the large end. 

It's important to note that what unarmored Celestials actually look like is up for debate. They may be energy creatures directly within the armor but it's also been theorized that the armors are avatars of creatures who live in another dimension. Also they tend not to stand on a surface but instead hover unless they specifically need to touch the ground (eg Eson slamming that planet's surface with the Power Stone). 

Due to the sheer level of power they wield they can disregard unimportant things like the gravity of the planet they're on/above. In the case of the 20,000 foot tall Exitar, he's been shown to be the size of Earth itself, so he isn't standing anywhere.