The modern city, however, was founded on July 25, 1641 as an "ostrog" on the Bely Iyus River. After the fire of 1683, it was moved to the Chulym River (a tributary of the Ob); hence, the official foundation date of the city is considered to be July 25, 1683. The name of the location derives from the Turkic tribal group Achi or Achigi. The first fort in 1683 was built with the high stockade square shaped walls. In the corners were placed watch towers. Initially the garrison had fifteen Cossacks patrolling it. In 1710, a new wooden fort on the right bank of the Achinki River was created, at its confluence with the Chulym.