Transcaspia

Transcaspia is an area of steppes and deserts (like Kara Kum) in Central Asia, between the Caspian Sea in the west, the Aral Sea in the north, the Amu Darya river in the north-east, and the Elburz and Hindu Kush mountains in the south.

The area more or less corresponds with the modern state of Turkmenistan. The adjective form is Transcaspian.