The land around the Ergene was nobody's idea of a good place to live. Swampy, choked with thorny vegetation that hid bandits and wolves, given to seasonal flooding that turned firm ground into impassable mire, it had stayed empty while people built villages on the higher hills nearby. But the river sat directly across the Gallipoli-to-Edirne road, the route Ottoman armies took when crossing into Europe. Every spring the river rose, and every spring the wooden bridges either disappeared or were burned by enemies. Sultan Murad II's chief architect Muslihiddin and the master craftsman Mehmed surveyed the soft clay and sandstone bed and concluded that only a long, low stone causeway would survive. The ground was first cleared of its thorn thickets — work that, by Ottoman accounts, also cleared out the highwaymen who used those thickets for cover.

There are still arguments about the exact length. Different surveys have given different answers as the river has shifted, as some arches buried themselves in silt, and as restorations have changed the structure. In 1978, surveyors measured 1,266 meters. In 1989, they got 1,254. In 2018, when the Guinness Book of Records sent its team, the answer came back at 1,306.2 meters. The Ottoman traveler Evliya Çelebi, who walked across in 1658, said it was 2,000 stretched steps long, which works out close enough to suggest he was not exaggerating much. Two viewing balconies were built into the parapet — one above arches 40 and 41, another above arches 102 and 103, the longer of the two stretching nearly ten meters. Places to pause, look down at the water, let a horse cart pass.

Earthquakes shook some arches loose. Floods undermined others. Over the centuries the bridge was patched and shortened and raised and patched again. In 1971, in an attempt at modernization that locals would later regret, the entire deck was widened to 6.8 meters and paved with steel and concrete, smoothing the old worn stones under a slick new surface that did the underlying structure no favors. By 2013 the cracks were visible enough that heavy vehicles were banned, and a separate concrete bridge was built a kilometer away to take the truck traffic. In 2018 someone at the Turkish Ministry of Interior tried to put a picture of the bridge on the cover of the new national passport, and accidentally used a photo of the wrong bridge entirely — the Meriç in nearby Edirne — while still labeling it Uzunköprü. The mistake made the news for a week.

When the 2021 restoration began, one of its goals was to dig out arches that had sunk into the riverbed and silted over, returning the bridge closer to its original profile. Workers also planned to pull up the asphalt and replace it with stone, and to replace any blocks that had cracked or fallen out. The bridge waits on UNESCO's tentative list for World Heritage status, a recognition that this is something more than a regional monument. It is among the longest stone bridges humans ever built before the industrial age. The figures and motifs carved into individual stones — animals, geometric patterns, family marks left by the masons themselves — were replaced over the centuries as stones wore out, so what stands today is layer on layer of repair, a stone bridge as palimpsest, still carrying weight.