500 Years Later, MIT Recreates Leonardo da Vinci’s Bold Bridge — And It Would Have Worked

Researchers at the Massachusetts Institute of Technology have recreated and tested a centuries-old bridge concept by Leonardo da Vinci, demonstrating that his daring single-span masonry arch for the Golden Horn was structurally sound in principle.

Leonardo’s Unusual Proposal

In the early 1500s Leonardo da Vinci submitted a design to Sultan Bayezid II for a crossing between Constantinople (today Istanbul) and the Galata district. Unlike typical bridges of the era, Leonardo proposed a flattened, single masonry arch roughly 918 feet (218 meters) long — high enough to allow tall sailing ships to pass beneath with masts intact. If built, it would have far exceeded the length and audacity of contemporaneous bridges.

Why the Design Stood Out

Beyond its span, the plan included features unusual for the time. Leonardo drew extended abutments or "wing walls" projecting from the sides to stabilize the structure against wind-induced lateral oscillations — a problem that has felled bridges even in the modern era. He described the structure as a masonry bridge that would rely on gravity and compression rather than metal fasteners or mortar to remain standing, a strategy inspired by ancient Roman arches.

How MIT Tested the Idea

MIT researchers — including graduate student Karly Bast and professors John Ochsendorf and Michelle Xie — examined Leonardo's sketches and letters (found in Manuscript L, held at the Institut de France), period construction methods, and the Golden Horn's historic geography. To test the geometry rather than historical construction techniques, they built a 1:500 physical model from 126 3‑D‑printed blocks, roughly three feet long, assembled without adhesives so that the assembly depended entirely on compression.

"I, your faithful servant, understand that it has been your intention to erect a bridge from Galata (Pera) to Stambul… across the Golden Horn ('Haliç')… It will be a masonry bridge as high as a building, and even tall ships will be able to sail under it."

The crucial test came when the team inserted the keystone. As Bast recalled, inserting that final stone and then removing scaffolding produced the decisive moment: the arch held. The researchers emphasize that the model was a test of geometry and load paths, showing that the design transfers forces through compression alone.

Findings and Caveats

Additional experiments suggested the arch geometry would have afforded greater earthquake resilience than most bridges of Leonardo’s time, and that the wing walls would have helped stabilize the span in high winds. However, uncertainties remain: Leonardo's surviving sketch could have been a quick concept drawing or a carefully worked engineering proposal, and the model does not prove the practicality or cost of building a full-scale stone bridge in the 16th century.

This project highlights Leonardo's advanced understanding of structural geometry and shows how historical designs can be reexamined with modern tools to test long-standing questions about feasibility.