The so-called Celestial Realm.
The so-called Netherworld.
Generally speaking, they belong to a metaphysical existence, differing from the real-world dimensions, entirely another dimension domain's mystery. Thus, the Celestial Kingdom is not above the atmosphere, nor can hell be dug out from the depths of the earth. The afterlife and the world above are not distanced from reality merely in physical terms.
However, now this is the Age of Gods...
The Netherworld and the present world are connected by soil. This afterlife indeed exists beneath the Mesopotamian earth, a subterranean space unimaginable from a geological perspective.
Even using the straightforward and brutal method of the Ishtar Goddess, descending to the Netherworld would involve blasting through the ground in one breath and jumping straight down.
