Qa'in

Qa'in (Qayen), in the Quhistan region of eastern Iran (modern South Khorasan), was a town of the historic Quhistan district, an area with a strong Ismaili presence in the medieval period. The polymath Nasir al-Din al-Tusi (d. 1274) was connected to Quhistan, spending part of his career under Ismaili patronage in the region before his years at Alamut.