Arch of Ctesiphon: Clock is ticking to preserve 1,700-year-old ancient arch in Iraq

Neglect and climate change has left the largest single-span bridge in the world nearing devastation, but a stabilisation project hopes to prevent catastrophic collapse

The Arch of Ctesiphon was once part of a larger palatial complex in the Persian empire’s capital. Courtesy Aliph

For 800 years, the ancient city of Ctesiphon served as a capital to the Parthian and the Sasanian empires. Sitting alongside the Tigris, south-east of present-day Baghdad, the city was one of the richest of its day, with a palace extravagantly decorated in marble, glass mosaics and jewel-adorned carpets.

Connecting two wings of this royal complex was an enormous parabolic arch, made of bricks and mortar, measuring 37 metres tall and 48 metres long. Even today, 1,700 years later, it is still the largest single-span bridge in the world.

But that impressive record might be nearing its end. Bit by bit, the Arch of Ctesiphon, or Taq Kasra, is falling down. The culprit isn’t conflict or looting – typical suspects for most Iraqi heritage sites under threat – but sustained neglect and climate change. Substantial portions fell in 2019 and 2020, and last month, after 20 days of torrential rain, a sizeable chunk dropped into a heap of rubble.

But thankfully for the beleaguered arch, plans were already in the works to keep it from collapsing. One evening in October, Swiss agency Aliph, which provides emergency funding for threatened heritage sites, received a call from Iraq’s Ministry of Culture about the state of the arch. The next day, it had convened a group to address it, and has now announced $700,000 towards stabilisation measures.

“Right now, we’re in emergency room triage,” says Michael Danti, project manager for the restoration team, a collaboration between two programmes at the University of Pennsylvania and Iraq’s State Board of Antiquities and Heritage. “We want to understand what’s happening, and get the scaffolding in place for the safety access and support, so that we can prevent any catastrophic collapse.”

The university’s Consultancy for Conservation and Development sent two architects to the grounds of Ctesiphon. An expert from Iconem, the Paris agency that documents threatened heritage sites, also mapped the structure. The data collected will become 3D visualisations that researchers can work on from their labs.

Danti, who leads Penn’s Iraq Heritage Stabilisation Programme, explains that the first task is to design scaffolding flexible enough to adjust to the movement of the walls, as they shift in size owing to temperature fluctuations. After the scaffolding has gone up, the long-term assessment will start, much of which has to do with understanding how the arch is responding to a new climate.

“We’ll install what are called crack monitors in the walls in the barrel vault, so that we can look at how those cracks expand and contract over time,” says Danti. “Then we can see whether some of them are just opening and closing with humidity and heat variations – the diurnal temperature variations in Iraq are extreme – or whether they are more alarming, and progressively getting wider. Once we understand the dynamics of the monument, we can look at more sustainable long-term solutions.”

The arch was once part of a larger palatial complex for the Persian empire’s capital, including an important library that was destroyed in the seventh century. It connects two buildings: a Sasanian-era wing and a Saddam Hussein-­era renovation on the right. Archaeologists believe the arch’s remarkable size is down to its unique lean: rather than being built across a flat span, as most masonry-built arches are, there is a 15-degree tilt towards the back, which supports the structure. Those bricks at the rear have now fallen, meaning the arch is leaning backwards into nothing.

The precarious state of the structure is well known, and there have been numerous past attempts at stabilisation. But, if there were ever a propitious time to save the arch from crumbling, this might be it. A number of initiatives emerged over the past seven years in response to the immense destruction to antiquities and heritage sites in the north of the country under ISIS and the subsequent fighting.  

Initiatives such as Aliph, which was launched in Abu Dhabi in 2016, allow immediate response to threats to heritage sites. With resources at hand, it does not need to fundraise to answer calls for help such as that by Iraq. “People in cultural heritage want to talk about ‘nimble response’,” says Danti. “This is nimble.”

But Danti acknowledges that the arch’s stabilisation is only one part of the project. The $700,000 will only take them so far and, over the next year, the team need to put forward their assessment so they can begin fundraising for a long-term plan. They also want to use the opportunity to train young archaeologists and researchers in Iraq, with the goal of making the country less reliant on outside expertise.

“Iraq was closed off for a long time, where their experts were not allowed to travel, or to seek education outside of Iraq, and foreign experts and students weren’t allowed to go there and meet their peers,” says Danti. Cultural heritage is “about these international efforts. And we’re trying to make up for lost time.”

Local stakeholders are another priority for the University of Pennsylvania team. Even setting aside the highly unethical aspects of early archaeology, the practice as it continued through the 20th century bears shades of colonialism, with western professionals overriding local stakeholders. The problem continues to this day, though responsible archaeologists and cultural heritage practitioners are working concertedly to address it. As with much of the reconstruction efforts currently taking place across Iraq, particularly in the northern areas that were heavily damaged by ISIS, the team at Ctesiphon emphasise engagement with nearby communities.

“We are there to facilitate the efforts of the Iraqi State Board of Antiquities and Heritage,” says Danti. “We’re not there to tell them what to do or necessarily how to do it. We’re there because we also value Taq Kasra in terms of what it represents for human achievement. But we also understand that that starts at a grass-roots level: the Iraqis’ interpretations of the site and the way they incorporate it into their daily lives. We’re going to work with what the State Board of Antiquities and Heritage wants, what the Iraqi people want, and move out from there, rather than a top-down approach.”

This includes understanding how the arch was used by the local community. For those in the area of Madain, the city nearest to the Ctesiphon ruins, the arch and its surrounding buildings were a popular picnic spot. “The monument could be preserved,” says Danti. “But if it doesn’t meet Iraqi expectations, if it doesn’t meet local stakeholder expectations, then I would feel that I failed.”