Nature: Abyssal civilization, a miniature

What if human evolution took place under the sea?

Hundreds of millions years ago, some life forms came out of the water and evolved on the surface of our planet, but many others evolved in the oceans. 

I pictured a world where humanity evolved under the sea, exploring the depths of a very different world, building vast cities shaped keeping in mind natural elements seen in this colorful environment.

I decided to represent this world as a miniature, in form of a diorama. Every zone has its depth reported in meters. The 2 zones on top (the farthest from the abyssal civilization) have no depth reported, becouse i thought it would have made the design too heavy. 

The metropolis stands out inside of an artificial crater, a smaller city can be seen not far away...

Model's size: 39studs x 29studs x 20 bricks (max size for contest is 64 x 32 x 60)