“No architectural plan for a city in any ancient site in the world, and particularly prehistoric sites, has ever been observed until the Achaemenid era. In fact, the sites had been small villages which had grown into cities due to an increase of the population, but the stratigraphy studies and research carried out by Iranian and Italian archaeologists indicate that this city had been constructed based on preplanning with precise and unique architecture,” Mansur Sajjadi added.

Located two kilometers from Qal'e-No village and about 44 kilometers from Zabol in Iran ’s southeastern province of Sistan-Baluchestan , the ancient city was identified by Italian archaeologists in 1960. They could not find any artifacts during several excavations from 1962 to 1965 but were satisfied with their architectural studies of Dahaneh Gholaman. A group of major monuments and some individual buildings were discovered at the site, which covers an area of 120,000 square meters.

“The inhabitants and engineers of the time used all their tools and facilities in the construction of the city, and the large size of buildings indicates the city had been an industrial city,” Sajjadi said, adding that the city may be the only Achaemenid site in which private residences are adjacent to public and governmental buildings.

“There is no private house beside the royal buildings in Persepolis which is indicative of Achaemenid architecture,” he noted.

“The Achaemenids used architectural plans only in the construction of palaces and important buildings in Persepolis and Pasargadae , but the inhabitants of Dahaneh Gholaman even used to prepare an architectural plan for the construction of an alley or a very ordinary house,” Sajjadi said.

Studies in the 1960s indicated that the residents abandoned the city about 200 years after it was founded and may have relocated to present-day Pakistan . However, the reason for the planned abandonment of Dahaneh Gholaman is still a mystery.

Archaeologists have surmised that the city was abandoned due to an important political decision, a strong sandstorm, or because the river which supplied water for the inhabitants ran dry.

According to Sajjadi, the best hypothesis to explain the sudden migration is that the river ran dry.

“It is likely that one of the branches of the Helmand River , which supplied water to the city, ran dry for some reason, and thus the people had to leave the city, but this is not certain,” he said.

The team of archaeologists is still trying to determine why the people abandoned the city in such a planned and systematic way.