Kafir Qal'a, also known as Zadiyan Qal'a, are the ruins of a citadel surrounded by a large agricultural enclosure north of the village of Zadiyan. Recently, archaeologists have used historical evidence combined with Carbon-14 dating to propose that the original foundation of the settlement occurred during the (ca. 1st century BCE - 1st century CE). The Carbon-14 dating and other architectural features demonstrated that the structure was in use for centuries after. At least some renovations likely occurred in the Kushan or early Sasanian period (ca. 3rd - 4th c. CE), and the citadel was still in use and modified as late as the Samanid and Ghaznavid periods (ca. 9th-11th c./3rd-5th c. AH), possibly up until the Mongol invasions in the early 13th/7th c. AH.

The agricultural enclosure surrounding the citadel of Zadiyan Kafir Qal'a takes the form of a perfect square measuring about 4 km per side, encompassing around 1600 hectares. The northern limit of this square is marked by the remains of a wall, still standing in areas up to 7 m high, which turns at a sharp right angle and runs to the south for around 1 km, marking its eastern boundary. Even where no walls remain standing, the boundaries of the enclosure are evident by the presence of a grid which emerges in aerial photos. This grid, visible in features in the landscape such as field boundaries and water channels, is composed of squares approximately 250 m per side. It ends at the northern and eastern walls, and abruptly in lines parallel to these on the western and southern sides of the large square, strongly suggesting that walls existed here too. Further suggesting that walls encompassed the entire square is the presence of a mound known as Pit Qal'a, located exactly half way down what would be the square enclosure's western boundary. This is presumed to have been a gate.

There is little evidence of development in this large square enclosure aside from the remains of a stupa and some associated remains in the southern half. It is thus likely that it served as an agricultural area for the central citadel.

In the exact center of the large square agricultural enclosure lies the site's central component: a fortified citadel about 200 x 200 m with walls preserved up to 12 m. A ditch surrounded these walls, and a bent-access gate provided an entrance on the west side. The location of this bent access entry gate is aligned precisely with Pit Qal'a, the presumed gate on the no-longer-extant western stretch of the agricultural enclosure wall. Along the southern walls of this square citadel are the ruins of Abu Hurayra, a domed Islamic khanqah-mausoleum dated tentatively to the Samanid period.

The chronology of the complex is still problematic and requires more research. A foundation during the Kushan period (ca. 1st c. BCE - 1st c. CE) is likely based on the ceramic evidence, which contain no Hellenistic ware, and the fact that the site is aligned with the old ford in the Amu Darya to the north at Kampyrtepe, which functioned until around 150 CE, when the city flooded and it was abandoned.1 C-14 dating of bricks in the wall surrounding the large agricultural enclosure confirm this date, suggesting a foundation during this period and a later renovation during the end of the Kushan or beginning of the Sasanian period. Another C-14 sampling of a brick from the central citadel suggests a date of the late 9th - early 11th c. /late 3rd - early 5th c. AH. This confirms a medieval Islamic phase, but leaves the question of foundation open, as the symmetrical layout of the entire complex suggests a unified composition.2

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Sources: 

De la Vaissière, Étienne, Philippe Marquis, and Julio Bendezu Sarmiento. "A Kushan Military Camp near Bactra." In Henry Falk, ed. Kushan Histories. Literary Sources and Selected Papers from a Symposium at Berlin, December 5 to 7, 2013, 241-254. Bremen: Hempen Verlag, 2015.