Cultural coherence of architecture in Greater Khorasan from Bactria to South Khorasan in Iran during the Late Iron Age/Achaemenid period

Abstract Tappe Takhchar-Abad, near Birjand in south Khorasan, is a recently discovered and excavated almost circular adobe building with six towers, dating to the Achaemenid period. This article suggests that the architectural tradition of circular buildings and sites in the late Iron Age/Achaemenid period, in Greater Khorasan, apparently originated from Bactria in which most such sites have been reported.