Short answers, pulled from the story.
Karagiye near Aktau sits at 132 meters below sea level and marks the lowest elevation in the entire Caspian Depression. The highest point in the depression rises only 4 meters above sea level.
Parts of Kazakhstan and Russia hold its borders. In Kazakhstan, it covers Atyrau Region, West Kazakhstan Region, and Mangystau Region while Russian territory includes Dagestan, Kalmykia, Saratov Oblast, Volgograd Oblast, Astrakhan Oblast, and Stavropol Krai.
About 1,200 such formations exist within the Caspian Depression as revealed by Russian satellite photos across western Kazakhstan. One dome called the Chelkar Deposit reaches nearly 5 kilometers deep into the earth.
The Volga River flows into the Caspian Sea through this low-lying area and the Ural River follows the same path toward the water. Their deltas create extensive wetlands that support life in an otherwise dry landscape.
Two largest cities anchor this industrial activity with Astrakhan in Russia serving as a major hub and Atyrau in Kazakhstan functioning similarly on the Kazakh side.