アルダン川
Beketov was sent to the Lena River in 1631 and in the following year he and his Cossacks founded Yakutsk, which became a base for further expeditions eastward. He sent his cossacks to explore the Aldan River and further down the Lena, to found new fortresses, and to collect taxes from the locals. In 1640 he transported collected taxes to Moscow where at his arrival he was appointed Strelets and Cossack commander and in 1641 Beketov returned to Enisei Ostrog as the head of the fortress.