These sketches of a self-supporting arched bridge are found in Manuscript L of da Vinci’s Paris Manuscripts. They demonstrate da Vinci’s incredible engineering acumen; though untrained, he intuitively discerned that a parabolic arch with a wide base would offer more support than the designs of other bridges at the time. Though da Vinci gave measurements for the bridge’s length and height, these dimensions were never confirmed or modified because the design was never implemented. It is likely that these sketches were completed in approximately 502 CE, as he sent his letter to Sultan Beyazid II proposing this design in summer of 502 or 503 CE. These sketches are currently housed at the Institut de France in Paris.
Sources:
Atalay, B. (2013, January 22). LEONARDO’S BRIDGE: Part 2. “A Bridge for the Sultan”. Retrieved May 11, 2019, from https://blog.nationalgeographic.org/2013/01/22/leonardos-bridge-part-2-…
Books, Maps and Calligraphic documents in the Topkapi Museum. (n.d.). Retrieved May 12, 2019, from http://kilyos.ee.bilkent.edu.tr/~history/booknmaps.html
Da Vinci, L. (n.d.). Golden Horn Bridge designed by Leonardo da Vinci in 1502. Paris Manuscript L, Folio 65v and 66r [Photograph found in Manuscript L, Institut de France, Paris]. Retrieved May 12, 2019, from https://commons.wikimedia.org/wiki/File:Leonardo_Bridge.jpg
Photo is taken from Wikimedia Commons. It is a reproduction of a document that is in public domain due to its age and thus free to use.