What is Atlantis?
Atlantis exists mostly underwater, deep in the Atlantic Ocean. It's higher elevations end as small islands associated with the west indies as well as the azores. Almost all of the islands that connect to Atlantis are very small and uninhabited. Cave entrances tunnel down until they reach into Atlantis' protective dome.
Most of the inhabitants of Atlantis are human, mixed from the decendants of the Atlantans that lived there when it sank and "modern" humans who have, in one way or another found their way down. Ships and planes lost in what is known as the Bermuda triangle generally yield a fair number of survivors who are brought down to Atlantis by the bubble creatures that comprise the dome. English, Spanish and Portugese are the main languages of Atlantis.
The bubble creatures have domed Atlantis since it sank, saving the original inhabitants from death. They continue to save humans who enter the water and bring them down to the continent. Many of those venture through the tunnels that lead back to the surface and return to the life they left behind. Injured persons nursed back to health tend to say in Atlantis after they recover. Most tend to stay to pay back the perceived debt they owe for their recovery, intending to return to the surface "someday", but settle down and remain in Atlantis.
The bubble creatures themselves are a mystery. Why did they save the original inhabitants and give over their lives to remain to protect Atlantis from the water? They appear to breath water and give off air, which keeps Atlantis protected from the water and supplied with fresh air. Their needs are few and they communicate with the Atlantans through an emissary, currently an elderly magika named Esmeria. All the emissaries have been magiki, at least all that are remembered by the Atlantan Council of Elders.