What is "niphates"

Niphates is a mountain chain in Armenia that John Milton uses in Paradise Lost iii. 742 as Satan's landing spot upon Earth. Milton is noted for his extensive use of obscure geographical references in his works.

Virgil also mentions the Niphates in the third book of his Georgics: "I will add the subdued cities of Asia, the beaten Niphates, / The Parthian who relies on his escape and backward arrows" (3.30).