An important eastern outpost of the ancient Khorezm is the largest fortress Janbas Kala (200x170m), located 47km north-east of Turktul. Founded in the 4th century BC the fortress has an archaic fortification system but without any defensive towers. The external corrugated walls up to 20 meters tall are well preserved and have over thousands of loopholes for archery. During an the attack against the fortress archers were placed on three levels: the upper open level, hiding behind high "battlement" of the walls, and two indoor levels within the corridors between the outer and inner wall. The gates with a labyrinth are located on the north-west side. The main street cutting the garrison and living blocks led to the south-east from these gates to the Temple of Fire.
In the 1st century BC Janbas Kala was taken by an offensive through the broken wall to the west of the gates and after that was never restored. For two millennia, the fortress was covered with sand dunes and only in the 20th century was excavated by Khorezm archaeological expedition.