I still don't understand where that golden barrier and the characters/ships are located exactly during the additional impact.
The hole leading to the minus space (from which Lilith emerges) is located in an "underworld" beyond the gates of Hell. Both gates seem to be constantly open. The gate of hell has multiple layers of protection though.
The underworld is enormous and goes insanely deep; the black moon is dozens of km tall and looks tinny inside of it. It's probably not physically located under the surface of the earth, otherwise its depth would crush everything. It's probably some other dimension connected to our world through the gate of hell, similar to the gate of guf.
So three options:
1) The whole additional impact happens underground with the golden barrier delimiting this "underworld" (nobody is shown "exiting" this place during the impact, outside of the life boats and the purple eva infinities going up and flooding the surface of the earth). But it doesn't explain why we see the moon during the additional Impact.
2) For some reason or another, everybody exits the underworld (but it would take some steep climbing and lots of time) and the impact happens outside, on the surface of the earth. I don't think it's the case, it would require Lilith to climb up that underworld and she would be so big you couldn't even spot the Wunder next to it. The scene where it goes through her hands and throws the spear inside her eye makes no sense in this scenario in terms of scale. Also, the four crosses don't appear anywhere.
3) For some reason the additional impact fuses the underworld and the surface of the earth, superposing the gate leading to the minus space to the gate of Hell. Since we see the moon (and probably the sun as well) during the additional Impact, I tend to think that's what probably happens, but it seems, yet again, very convoluted for no good reason.
Please tell me I'm not the only one who's been obsessed with the place's topology during the last part of the movie, I once made a thread about it but it wasn't very popular
edit:
Apparently the door leading to the minus space is the door of guf: