In 1557, at the request of local businessmen, the Turkish architect Hayrudin was employed by Suleyman the Magnificent to build a stone bridge in Mostar. It would replace the suspension bridge which was said to frighten tradesmen as they swung and wobbled their way over the fast-flowing Neretva River.

Mostar’s Old Bridge took nine years to build and was opened some time between July and September in 1566. It was built out of local Tenelija stone, which is light-coloured and appears to change colour depending on the position and the strength of the sunshine. The bridge’s single span of almost 29m was distinguished by its slender and elegant shape, the arch rising 20m above the lowest water level.

Local history contains many myths surrounding the construction of Old Bridge – one of the favourites is that Hayrudin was so afraid that the bridge would collapse once the scaffolding was removed that he fled to the nearby Dervish monastery and never saw the completed structure. By contrast, another story tells how, after the scaffolding had been removed, he had to lie under the bridge for three days, risking his life to prove the structure was stable. Whatever the truth, the bridge stood for 427 years.

The engineers rebuilding the bridge are due to remove the scaffolding next summer; whether they will take similar measures to Hayrudin to prove its stability is unknown, but the reopening is awaited with baited breath. The bridge was destroyed in November 1993 so it will have taken more than ten years to achieve the rebuilding. Eventually funding from World Bank and various countries such as Italy, Turkey, Croatia, Council of Europe Development Bank, and the Dutch government allowed the project to take off. The final stone was laid in August this year and the bridge will be reopened once the towers have been rebuilt on each bank. The Turkish contractor Er-Bu, which specialises in the reconstruction of stone bridges mostly from the Ottoman period, is carrying out the entire building project, including the stone masonry. Croatian engineering firm Omega Inzinjering, which specialises in cultural heritage monuments, is supervising the work.

Er-Bu and Omega Inzinjering found themselves with a mighty challenge and an even mightier puzzle on their hands. Quite apart from the expectations of Mostar’s citizens, the structural reconstruction challenge was overwhelming. The new bridge had to be identical to the Old Bridge, hence the bridge had to be rebuilt using the 16th Century methods, without the interference of modern building methods. The length of the main span of the bridge is 28.6m, and its width is 396cm.

According to Omega Inzinjering supervisor Zeljko Pekovic, the main challenge was determining whether the bridge would be structurally sound. "The static analyses were dubious about this despite the fact that the bridge had already been standing for almost 500 years. We thought about reinforcing it, but we had decided to build it as it had been built before and with the help of numerical models and calculations we managed to prove that it needed no reinforcement or modern materials."

Another big challenge was in the scaffolding - the only part of the bridge which could not be traced back to Hayrudin as there were no detailed records of the construction process. The bridge is being built using limestone and sand mortar, a combination which takes a long time to harden, and it was crucial to build scaffolding which could support the construction and resist the powerful hydraulic forces caused by the river crashing against the abutments. "Work had been done on the foundations in the previous years, and the abutments did not need any major work, so the scaffolding was really the most important and difficult part of the project," says Pekovic.

Another puzzle presented itself in the old stone construction work. In ancient times stone was quarried and cut using average measures and the results depended largely on the quarry’s natural availability. Stone was assembled onto the centring almost randomly, taking into consideration a few factors such as stone joint shift, the overall thickness of the load bearing arch, the width of each row and the need to keep each row parallel.

So although the original bridge was soundly built, it was not regular, and the anomalies created by this method of assembling the voussoirs, were at the same time both the real beauty of the bridge and the origin of its complex geometry. In the rebuilding, however, this random assembly had to be replicated; in order to recreate the shape and the imperfections, each stone had to be cut separately to its own particular shape and planned position.

Contractor Er-Bu’s experience in traditional stone masonry was invaluable, and an added saving grace was a photogrammetric picture of the bridge’s internal and external structure taken during restoration work in 1982. The engineers discovered that the stone blocks of the Old Bridge, with its unsupported length of deck at almost 29m, were reinforced by cramps and dowels made in hand-forged iron and placed across the joints. For the reconstruction, each stone was drawn and numbered separately, and this enabled smooth progress to be achieved.

The same type of stone from the same quarry was used for the rebuilding project. Tenelija stone has good mechanical properties – it is light and it is resistant to damp and frost. The original stone blocks which had fallen into the river in 1993 had become unusable by the time they were recovered in 1996. The relatively soft stone blocks had been eroded and the metal connections had rusted and created cracks that had rendered the old stone unusable. However, part of the old Old Bridge has been saved – on the west bank of the Neretva, five rows of stone and the whole of the abutments. "We will also be able to use some of the original material to build the parapet, and for parts of the construction which are not of key importance," says Pekovic.

As a ‘once in a lifetime’ opportunity, Pekovic says that the bridge project was a major challenge for the consultants and contractors alike. The possibility of rebuilding the bridge to a new design was never an option, he says. "This is such a valuable monument, such an important symbol that nothing could ever be built in its place."

Work has now started to rebuild the towers on each side of the bridge; Tara on the east bank and Halebija on the west. The two towers, one of which was once where local intellectuals and spiritual men debated their ideas, were the bridge’s original companions, so the crossing will not be reopened until they are completed. The ceremony, with the traditional annual diving competition, is expected to take place in summer 2004.

CENTRE OF ATTENTION

Before its destruction, the Old Bridge was a central focus in Mostar; it was a meeting point; it had the river beneath for swimming in, the food market next to it, and on summer nights was surrounded by swarms of youngsters in local bars.

One event that really drew the crowds was the annual diving competition, which has been held in August every year for the past four centuries. All young Mostarians strive to fly gracefully from the top of the arch, into the cool Neretva below. Boys start by diving off the rocks below the bridge and as they grow older and more confident, they progress onto the bridge itself, diving for money or cigarettes. When you dive off the top of the bridge, you know you have become a man, or ‘Mostar’s Icarus’.

During the war, Mostar’s six other bridges were destroyed, and the Old Bridge was the only one remaining. Muslims used it to bring supplies back and forth, to go to the front line, and bring back the dead and wounded. The bombing of the bridge in 1993 was partly a strategic act, but also a symbolic destruction of what the bridge represented: beauty, unity, and history. Mostar housed Christians, Muslims and Jews alike, but when the bridge was destroyed, it became a divided city. With its reconstruction, the people of Mostar are being reminded of how they used to live, and how they might live again.

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