Atlantis

Atlantis was the home of the Atlanteans, which were the fourth Root Race and were the first 'true' civilised Humans as the first 3, the Lemurians, Hyperborean, and Ethereals, were reproducing by laying eggs, or, in the Ethereals case, were not even physical beings.

The Atlantean Empire
The Atlanteans controlled much of North and South America and some of Europe and Northern Africa. It is believed that when the Atlantean Empire fell, they left behind the first primitive homonids, Austrolopithecine, which eventually gave rise to modern day homo sapiens.

Total Assault 3
In Total Assault 3, Dark Energy somehow activated a mechanism that caused the Island to rise out of the ocean once more, Robbie described it, "it was as if Atlas himself had lifted it out himself." After this, the MSWG stormed the Atlantean Citadel only to find Dark Energy himself driven insane by The Metatron's poisoned words. They were then attacked by Bogart himself, and they then followed him through the portal. Much of Atlantis' surface was singed black along with North America by the Harbingers as they fired their weapon to destroy the Spawn.