Da Vinci Bridge - Made with Pencils and Rubber Bands

Leonardo da Vinci proposed a bridge 240 m (790 ft) long, overall and 24 m (79 ft) wide over the Golden Horn in 1502 for Sultan Bayezid II of Constantinople (today's Istanbul). The sketch and letter proposal were lost for over 400 years before being rediscovered in 1952.[The proposed bridge included a 240 m (790 ft) "pressed bow" main span with 43 m (141 ft) of vertical clearance to allow ships to pass.[2][3] da Vinci bragged that "it has been [the Sultan's] intention to erect a bridge from Galata (Pera) to Stambul… across the Golden Horn (‘Haliç’), but this has not been done because there were no experts available. I, your subject, have determined how to build the bridge. It will be a masonry bridge as high as a building, and even tall ships will be able to sail under it." The sketch was confirmed to be a genuine work of da Vinci by comparison with an identical sketch in Manuscript L, part of the Paris Manuscripts stored in the Institut de France in Paris.

Had the 1502 design been implemented, it would have been the longest bridge in the world,[5] and it would still be the longest single masonry arch span in the world. Da Vinci is said to have been inspired by the then newly built bridge "Ponte degli Alidosi" over Santerno at Castel del Rio near Bologna with a 42 m high semicircular arch.

In 2019, a research team at the Massachusetts Institute of Technology tested the stability of da Vinci's design by building a 1:500 scale model using only blocks without using fasteners or mortar, replicating contemporary masonry construction techniques. The bridge was first analyzed using a 3D model, then divided into 126 individual blocks which were individually printed, consuming approximately 6 hours per block. Falsework was used to temporarily support the blocks during construction of the scale model. After the falsework was removed, the model proved to be stable under load, and the spread-footing design proposed by da Vinci was able to resist movement of the foundation.