In 1502, Leonardo DaVinci submitted a design for a bridge to Sultan Bayezid II. This bridge design would have been the longest in the world at 280 meters and was sent due to a request from the Sultan of the Ottoman Empire for a bridge to span the Golden Horn and connect Istanbul to Galata.  Leonardo’s design was not selected as he provided only the designs and no instructions on how to build it. Leonardo heard about the request after returning from French invasion of  Milan in 1499 to Venice and meeting Turkish merchants who mentioned Bayezid’s bid. His design was of one long, flattened curve higher than the boats to pass underneath it that allowed for self-sustaining geometry, as opposed to the many arches of bridges of the medieval period. He used multiple geometries, such as the parabolic curve, pressed bow, and keystone arch to stabilize the bridge despite not having support beams. Leonardo also proposed a cable bridge across the Bosphorus Strait.

In October 2019, engineers at MIT decided to test DaVinci’s design with a scaled model. The team built a model with a 1:500 scale, resulting in a 32-inch model. The model used materials that the engineers assumed would be used, such as stone and lacked the use of mortar. The engineers concluded that the design would have worked and would have been capable of surviving even earthquakes, but do not know how much of it was intentional and how much was pure coincidence of his choice. Either way, this demonstrates Leonardo’s genius and superior understanding of geometry.  

See also, Katlenn’s post

Chandler, David L. “Engineers Put Leonardo Da Vinci's Bridge Design to the Test.” MIT News, Massachusetts Institute of Technology, 9 Oct. 2019, news.mit.edu/2019/leonardo-da-vinci-bridge-test-1010. 

Daley, Jason. “Scientists Prove Leonardo Da Vinci's 500-Year-Old Bridge Design Actually Works.” Smithsonian.com, Smithsonian Institution, 16 Oct. 2019, www.smithsonianmag.com/smart-news/da-vincis-unbuilt-super-long-istanbul-....

TRTWorld. “Leonardo Da Vinci’s Future-Proof Design for an Istanbul Bridge.” Leonardo Da Vinci's Future-Proof Design for an Istanbul Bridge, TRT World, 29 Nov. 2019, www.trtworld.com/turkey/leonardo-da-vinci-s-future-proof-design-for-an-i....