Even though today's Renault logo is a double pyramid with both upper and lower pyramid tops cut off, the early logo was simply a diamond shape octahedron.
Look at this announcement of a Renault classics exposition. Are these Renault cars inside a concave earth???
Interesting, It just came back to me that Enki was the 'lord of the Waters' which also became intermixed with god of the 'underworld'. If his name came from a time-frame before the Earth had oceans then this 'Water' he was lord of could very well be the celestial ocean which would be the 'underworld' of the Heavenly city of Jerusalem in a sense.
The inference of 'water' was also fresh water, and not salty water like our oceans. This would also explain why the ice sheets are not opaque.