Conservationists, including the UN's heritage body, Unesco, say the 15.5m pound Sivand dam threatens the long-term survival of the historic tomb and the remains of several adjoining palaces at Pasargad in southern Iran.
The dam's opening has already been postponed by more than a year to allow international teams of archaeologists to dig in the neighbouring Tange Bolaghi gorge, where civilisation is believed to date back 6,500 years. Excavations have uncovered a wealth of remains, including remnants of a palace belonging to King Darius the Great, a successor to Cyrus, and an iron smelting plant traced back to around 2,500BC. The skeleton of a human female, originating from around 4,000BC was also discovered in a cave.
The gorge, thought to have been a hunting area for kings during the 2,800-year-old Achaemenid dynasty, will be flooded once the dam starts operating. Hundreds of hectares of farmland will also be swamped, necessitating compensation for local farmers.
The water authority insists the tomb will be unaffected but has offered to install humidity measuring devices to monitor possible damage."