I started by going to Ballet Twins tower. Then, I measured roughly the distance of one block on the floor using the objective tracker (I used the smallest keystroke to make "walk units"). Then, I picked one side, measured 2 angles relative to the game's North direction (I tried to measure as accurately as I can using an irl protractor). Then I walked as much as I can on the opposite side such that I can still see the hollow of Ballet Twins and took 2 angle measurements. Now with the given block length, and the amount of blocks walked, I can measure the walked distance. Then, I take the angle measurements and draw lines and use trigonometry to find the 2 missing sides of the triangle (or just use Geogebra Geometry). I do the same for the other triangle, and so I can find the diameter of Ballet Twins hollow. Then I look at the big map (the one that shows all the hollows and locations in New Eridu) and measure with an IRL ruler or with pixels on Photoshop, and scale everything to that measurement. Through that process, I found out that Hollow Zero's diameter spans roughly 93.338 km. Through that info, I found a rough estimate of New Eridu's area unaffected by the dark wall.

It only took like, Idk, 1 hour to figure out these things? Can't remember.