The Caspian Sea Nation is IRAN, which is a country located in the Middle East. It is bordered by Armenia, Azerbaijan, Turkmenistan, Afghanistan, and Turkey. IRAN is the largest country in the Middle East and has a population of over 80 million people. It is home to one of the world's oldest civilizations and has a rich cultural heritage. IRAN is also an important player in the global economy, with its oil and gas reserves being among the largest in the world.