Old game called Septerra Core
Back in its day it rocked... http://en.wikipedia.org/wiki/Septerra_Core
Setting and basic premise
The world's seven continental layers (referred to as "World Shells" or "Shells") shield access to the clockwork computer planetary core. Legends mention two "core keys" which, during a rare alignment of the shells that allows a beam of sunlight to penetrate through, can unlock the planetary core, releasing the "Legacy of the Creator". This legacy is known as the Kingdom of Heaven. Those living on Shell 1 call themselves "the Chosen". They are descendents of the demigod Marduk, son of the Creator, and have an attitude of superiority over other inhabitants of the planet. Those living on Shell 2 are called "the Junkers", people which make a living out of collecting junk - especially electronic - originating from the upper shell. The main plot is set around members of both shells. The game's main character is Maya, from the Junkers, and the main antagonist, Lord Doskias, comes from a Chosen heritage.