What bridge design did Leonardo da Vinci propose as a single broad arch?

Leonardo da Vinci proposed a self-supporting bridge formed from a single broad arch.

The design was created in the context of a proposal for Sultan Bayezid II, who sought a bridge across the Golden Horn near Constantinople. Leonardo’s drawing shows a wide masonry structure with an unusual flattened arch and supporting geometry intended to carry loads across the span.

The bridge was never built in Leonardo’s lifetime. Its significance lies in the way the design uses the shape and arrangement of the structure to create stability without the many small arches common in older bridges.

In 2001, a scaled model inspired by the drawing was constructed in Norway. It demonstrated that the geometry could work as a stable structure, although a modern model is not proof that every historical construction detail would have been practical with Renaissance materials.