The vast ancient area of Vigol located in the northern part of the city of ?r?n-o-Bidgol was identified by the authors of the present article in Autumn 2006 and underwent a systematic archeological study as a result of which remnants of the two independent cities were identified with two separate governmental castles. Since, apart from the said castles, other urban areas, works of architecture, and items of cultural elements were buried under flowing sand, archeological investigations were carried out with difficulty, yet due to the fact that the sands served as a means to protect the said pieces and works, items of the cultural elements were found in a relatively intact condition.
Nevertheless, the team managed, upon permission by the Archeological Research Center, to conduct an investigation on some 100 hectares of the mentioned cities. Chronological study of the surface data revealed that the two cities were inhabited since the Sassanid era up to the end of the Seljuk Dynasty in Iran, that is to say, the end of the sixth century after Hegira.
Following a brief introduction of the above two cities, the present study analyses the data derived from a field surveys on the settlement eras, form and functions of the cities, and where possible, the grounds underlying their decline.