With the Shaar on the east, it separated the Shining South from the rest of Faerûn. On its shores was a collection of free cities, mainly on the northern and western sides. The southern side, by contrast, was a collection of kingdoms collectively named the Border Kingdoms. At the center of the lake was the Arnrock. The mountains around the area were one of the only places that the rare substance, Zardazik, could be found.
The Lake of Steam is a large, enclosed bay of the Shining Sea. The region is extremely volcanic, such that a number of steam vents and fumaroles cause the sea to bubble and smoke along its length. Its islands are volcanic in origin, and its largest island, Arnrock, is an active volcano. The Lake of Steam has a large number of cities and towns along its perimeter. They are known in general terms as the Border Kingdoms. Little is known about these kingdoms, save that they trade with Vilhon Reach to the north and are continually battling with Calishite forces to the west. It is rumored that some of the cities, such as Mintar, are held under the sway of cruel and insane outcasts of magical Halruaa.
As of 1479 DR, the Lake of Steam was about half the size it was before the Spellplague. The Arnrock was in the eastern half of the sea rather than the center, and the eastern portion of the sea ended about thirty miles short of the town of Derlusk, where Derlusk was once on the southeastern coast of the sea. A large lake was separated from the main body of the sea and lay near the ruins of Innarlith. The Qurth Forest was a small fraction of its former size, and the Duskwood was completely gone. Suldolphor was also in ruins.