Wiktionary
tabaristan
n. The name of the former historic region in the southern coasts of Caspian Sea.
Wikipedia
Tabaristan
Tabaristan (from Middle Persian: , Tapurstān), also known as Tapuria, was the name applied to Mazandaran, a province in northern Iran. Although the natives of the region knew it as Mazandaran, the region was called Tabaristan from the Arab conquests to the Seljuk period.