Persepolis Unveils Innovative Conservation Program Utilizing Cutting-Edge Materials and Imaging Technology

Iranian restoration teams have embarked on an ambitious conservation initiative at the UNESCO World Heritage sites of Persepolis and Naqsh-e Rostam. This project utilizes cutting-edge technologies such as advanced imaging, specialized materials, and stone analysis to ensure the preservation of these ancient treasures.

According to officials, this conservation effort is being spearheaded by Iranian researchers with the backing of international scientific institutions. The work involves techniques like laser scanning, 3D imaging, and detailed structural analysis of stone surfaces. The use of environmentally friendly protective materials is intended to mitigate erosion and other environmental factors.

Persepolis, founded by Darius the Great around 518 BC, was the ceremonial capital of the Achaemenid Empire (circa 550 – 330 BC). Located approximately 60 km northeast of Shiraz, this monumental complex was largely destroyed by Alexander the Great in 330 BC. Today, its surviving palaces, stairways, and cuneiform inscriptions are among the most significant archaeological remnants of the ancient world.

The nearby Naqsh-e Rostam site, which includes royal Achaemenid tombs carved into the mountainside and rock reliefs from later periods, is also receiving attention. Mohammad-Javad Jafari, head of the Persepolis World Heritage base, indicated that Naqsh-e Rostam “requires immediate attention for emergency protection.” He noted that most archaeological research at the site was conducted in the 1950s, with subsequent efforts largely focused on preservation.

Recent studies from Shiraz University have revealed concerning findings, including land subsidence and ground fractures in the area surrounding Naqsh-e Rostam. Jafari emphasized that while these soil movements do not directly threaten the main rock-cut structures, they pose a risk to the foundations of some built features.

Experts have initiated a significant conservation project on one of the largest inscriptions at Persepolis, according to senior heritage conservator Shahram Rahbar. He mentioned that this inscription had never undergone restoration since its inception and had been spared from intentional human damage. The multi-year project will focus on:

• Stabilizing the rear of the inscription to prevent movement from earthquakes and other forces.
• Constructing a protective canopy to shield it from environmental elements.
• Treating the stone surface to ensure its longevity.

Rahbar noted that the restoration work requires precise handling of fragments and cracks, which includes making critical decisions about whether to reconstruct missing parts or stabilize them without reconstruction. Two specialists in ancient scripts are overseeing the grouting process, ensuring the utmost care is taken.

The materials used in this project are lime-based conservation materials that match the physical properties of the original stone. These materials are designed to be reversible and possess similar moisture absorption and thermal expansion characteristics, which is essential for maintaining the integrity of the ancient structures.

However, the application of these conservation materials comes with challenges. They are costly and can only be applied during specific times of the year—spring and autumn—when temperatures are between 5°C and 35°C.

Officials reiterated that these conservation efforts are critical to protecting Persepolis and Naqsh-e Rostam from weathering caused by wind, humidity, temperature fluctuations, and increasing tourist traffic.

Persepolis, located at the foot of Kuh-e Rahmat (Mountain of Mercy) in southwestern Iran, is one of the world’s most significant archaeological sites. It is celebrated as the finest ensemble of Achaemenid architecture, urban planning, construction technology, and art. The monumental city stands as a unique testament to one of the ancient world’s great civilizations. The construction of this vast terrace began around 518 BCE under Darius the Great, who was the king of the Achaemenid Empire.

Throughout the years, successive rulers, including Darius’s son Xerxes I (486–465 BCE) and grandson Artaxerxes I (465–424 BCE), continued to expand this impressive ceremonial complex. The site consists of:

• Grand approaches and monumental stairways.
• Throne rooms and reception halls.
• Auxiliary buildings that complement the main structures.

This 13-hectare ensemble is recognized as one of the world’s foremost archaeological sites. The terrace itself is an extraordinary architectural achievement, featuring double stairways, sculpted friezes, and Assyrian-style propylaea (monumental gateways). Additionally, gigantic winged bulls and the remains of vast halls further contribute to its grandeur.

Innovative engineering techniques employed by Achaemenid architects, such as lighter roofing and wooden lintels, allowed for the support of large open spaces with remarkably slender columns. These columns were adorned with elaborate capitals, most notably the double-bull capital, where the forequarters of two kneeling bulls—set back-to-back atop double volutes—extend their necks to brace the ceiling beams.

Although Persepolis served as a governmental seat for the Achaemenid Empire, it was primarily conceived as a ceremonial center for royal receptions and imperial festivals. As such, its grand terrace remains a symbol of Achaemenid kingship—a stage on which the king’s image is depicted in various forms, displaying victories over foes and presiding over tributes.