Rising from the heart of Istanbul, the Ayasofya Mosque has served as a bridge between empires, faiths, and centuries of human civilisation.
Now, Türkiye has launched one of the most extensive restoration efforts in the history of the republic — not only in response to possible risks but to protect the monument against the wear of time and ensure its survival for generations to come.
Architects, engineers, and heritage experts are working together to restore and stabilise key sections of the sixth-century structure, which has undergone repeated transformations and repairs over the last 1,500 years.
At the centre of the effort is Professor Hasan Firat Diker, an architect from Fatih Sultan Mehmet Vakif University and a member of the Ayasofya Mosque Scientific Committee, “We are not just responsible for this building but for the entire world public,” says Diker to The Guardian, gesturing toward the visitors kneeling on the turquoise carpets or gazing up at the feathered seraphim beneath the gold-covered dome.
Layers of history
Constructed in 537 during the Byzantine Empire, Ayasofya Mosque has served as a cathedral, mosque, and museum — a structure that has endured political, cultural and physical transformations.
Its massive dome, once the largest in the world, collapsed during an earthquake in 558, and surrounding semi-domes were damaged in later tremors. With each intervention, different architectural styles and solutions were added, creating a complex mosaic of structural layers.
“These reconstructions over different periods created layers of buildup on the dome’s surface … we know at the moment it’s not a perfect sphere due to the multiple interventions. The problem is not the dome itself but what is holding it up – for now. But when we uncover it, we will better see the cracks,” Diker tells.
The restoration team plans to remove the lead covering of the dome, examine the pillars supporting it, and reinforce the joints between the main dome and semi-domes. In addition, work will extend to the minarets and outer surfaces of the building.
“For the moment, we will deal with the outer surfaces, the minarets and the main dome. We will better understand after removing the dome’s lead covering,” says Diker.
Modern approach to preservation
On April 14, Türkiye’s Culture and Tourism Minister Mehmet Nuri Ersoy announced on his official X account: “We continue our restoration and reinforcement works at the Hagia Sophia Grand Mosque without interrupting prayers.”
According to the Ministry, the ongoing work is being conducted from the exterior of the dome to avoid any damage to the historic interior mosaics. The primary aim is to enhance the dome’s resistance to earthquakes while meticulously preserving its original structure.
To ensure that daily worship can continue uninterrupted, a 43.5-metre-high steel platform has been installed. The dome remains temporarily enclosed by a protective steel framework and tarp, with technical operations supported by a tower crane.
The ministry also confirmed the creation of a digital twin of Hagia Sophia, stating that earthquake risk assessments have guided the entire restoration process. “The historic dome will be handed down to future generations, preserved in its original form,” the ministry said.
This restoration is not only technical but philosophical. The team aims to extend the structure’s lifespan using minimally invasive methods while retaining its historical and spiritual character.
“This may be one of the greatest restorations of the current period in Türkiye,” Diker noted. “We need to care for the comfort of our visitors. Those who come here should be able to see as much of the Ayasofya Mosque as they can despite the restoration.”
Specially designed scaffolding and protective coverings will allow both worship and tourism to continue during the restoration. While the dome is being accessed, teams also hope to uncover hidden murals from the structure’s Ottoman period, currently concealed beneath more recent surface layers.
Though recent seismic activity has reminded residents of Istanbul’s vulnerability, the restoration is driven as much by the building’s long and layered history as by the potential for natural disasters.
“In the most terrifying scenario, an earthquake will shake the entire structure,” says Diker. “The main arch connecting the main dome and semi-domes could tremble and there might be cracks that occur.”
The monument is structurally uneven due to past reconstructions, and the dome rests atop columns of different dimensions.
The team is using modern tools, including 3D modelling and earthquake simulations, to understand and reinforce key structural points.
“These reconstructions over different periods created layers of buildup... The problem is not the dome itself but what is holding it up – for now,” Diker reiterated.
He also noted that an earthquake could cause a rare but dangerous “hammering” effect, in which different parts of the building collide due to movement during shaking.
“The main arch connecting the main dome and semi-domes could tremble. An earthquake could also jolt the minaret into the domes, or cause the arches to collapse entirely.”
Ilknur Turkoglu, a cultural heritage expert, said Istanbul’s seismic risk is well established.
"Though Istanbul does not sit directly on a major fault line, its surrounding region is highly active, causing significant earthquakes that have historically caused damage to the city, like the 1999 Golcuk and Duzce earthquakes,” Turkoglu tells Daily Sabah.
"With such a large and dense population, the damage and casualties from a similar earthquake today would be far greater,” she warns.
"Knowing exactly what we have is the first step,” says Turkoglu, who is also an assistant professor at the Istanbul Gelisim University’s Department of Architecture.
"Unfortunately, Istanbul still lacks a comprehensive inventory of its cultural assets, both above and below ground.”
"We need to conduct earthquake drills, ensure artefacts and display cases are secure and check that emergency systems like automatic shut-offs for electricity, gas and water are in place,” she says.
"Even if walls remain standing, unsecured objects inside can still injure or kill.”
"The situation following the 1999 and February 2023 earthquakes offered a preview," she adds, "of what could happen without better preparedness, including plans to protect or relocate valuable artefacts.”
Beyond time
The restoration of Ayasofya Mosque goes beyond physical repair — it is an effort to honour a legacy shared by all of humanity. Once the largest cathedral in Christendom, later a symbol of Ottoman architecture, and today a functioning mosque, the monument has long stood at the intersection of East and West.
Under UNESCO protection since 1985, Ayasofya Mosque is recognised as a site of outstanding universal value, and restoration efforts are being carried out in line with international conservation standards.
“We are not just responsible for this building but to the entire world public,” Diker emphasised again.
There is no fixed deadline for the project, but the intention is clear: to protect Ayasofya Mosque not only from future challenges, but from the slow erosion of time — and to ensure that its story continues to be told in stone, light, and space.
