The Cas or Caspi were a tribe of the Dahae who settled south of the Caspian sea and north of the Alborz mountains, in what is now the Gīlān Province, in Achaemenid times. The modern Gilaks are their descendants.^{[citation needed]} They are described as having light hair and blue or green eyes; in the Gileki language, caas-e-chum means blue or green eye. ^{[citation needed]} Ideograms for Ta-Hsia. ... The Caspian Sea is the largest lake on Earth by both area and volume,[1] with a surface area of 371,000 square kilometres (143,244 mi²) and a volume of 78,200 cubic kilometres (18,761 mi³).[2] It is a landlocked endorheic body of water and lies between... Alborz Mountains underneath clouds seen from Tehran Alborz (in Persian البرز), also written as Alburz or Elburz, is a mountain range in northern Iran, stretching from the borders of Armenia in the north-west to the southern end of the Caspian Sea, where also Tehran and Irans highest peak, Damavand... Achaemenid Empire The Achaemenid Dynasty was a dynasty in the ancient Persian Empire, including Cyrus II the Great, Darius I and Xerxes I. At the height of their power, the Achaemenid rulers of Persia ruled over territories roughly emcompassing some parts of todays Iraq, Egypt, Syria, Jordan, Israel, Lebanon... Gilak or Guilak are the people who are born in Guilan. ...

The Caspian is named after them, as well as the cities of Ctesiphon and Qazvin Ctesiphon, 1932 Ctesiphon (Parthian and Pahlavi: Tyspwn as well as Tisfun, Persian: ‎, also known as in Arabic Madain, Maden or Al-Madain) is one of the great cities of ancient Mesopotamia and the capital of the Parthian Empire and its successor, the Sassanid Empire, for more than 800 years... Qazvin may refer to: Qazvin (city) Qazvin province Note: Qazvin province was created in 1996; older references to Qazvin are invariably to the city. ...