Changing Planet

LEONARDO’S BRIDGE: Part 2. “A Bridge for the Sultan”

Portraits of Fatih Sultan Mehmet and Sultan Yildirim Beyazit

I once heard of a tradition in Turkey that Leonardo was invited to Istanbul to paint a portrait of “Mehmed the Conqueror” (Fatih Sultan Mehmet) but was unable to accept the commission. No documentation exists to corroborate this story. But there is manifest evidence of Leonardo’s contemporary, the Venetian painter Gentile Bellini, journeying to Constantinople and painting the defining portrait of the Sultan familiar to all Turks. Dating to 1480, it now hangs in the National Gallery, London.

In 1500, after the French invaded Milan and imprisoned Leonardo’s patron, Ludovico Sforza, Leonardo found himself out of a job. Accompanied by his mathematician friend Fra Luca Pacioli and his own feckless assistant Andrea Salai, he left Milan and set out on the road in search of new employment. He traveled east to Mantua and Venice, and worked for a time in Venice as a military engineer. It was in Venice that he apparently came into the circle of merchants trading with the Ottomans. By 1503 he had also abandoned Venice, and for a time served in the employ of the notorious Cesaré Borgia. Then, with the assistance of his friend Niccolo Machiavelli, he had secured a commission that would pit him against his arch-rival, Michelangelo. The two titans of the High Renaissance were to paint a pair of immense murals side-by-side in the Pallazo dela Signoria in Florence. Like so many projects during his career, however, his mural, the “Battle of Anghiari,” would also fall by the wayside. But in 1502-1503 Leonardo applied for a position in the Court of Fatih Sultan Mehmet’s successor, his son Sultan Bayazid II, an enlightened leader who is known for welcoming into Ottoman lands Jews expelled by Spain in 1492.

The letter discovered in 1952 in the Topkapi archives. Sent by Leonardo, it was received in the Ottoman Court of Beyazit II (1502-1503), and mistakenkly attribution to “Ricardo of Genoa.”

In his letter Leonardo proposes four separate projects to the Sultan:

•  “I have a design for a gristmill powered by wind, without the need for running water.” (Nothing new here! Two hundred years earlier the Chinese made windmills, and six hundred years earlier, the Persians. And well before either of them, Heron of Alexandria in the 1st Century AD is thought to have made a working windmill.)

• “I have developed a bilge pump to remove water without the use of ropes and pulleys,” wrote Leonardo.”  (Here he has a hydraulic apparatus in mind, and drawings exist for that purpose among his notebooks.)

• “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”), 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.” This bridge is the subject of the present story.

• “I plan to build a suspension bridge across the Bosporus to allow people to travel between Europe and Asia. By the power of God, I hope you will believe my words. I will be at your beck and call at all times. — Architect/engineer Leonardo da Vinci” (The letter is dated 3 July, but the year is not specified.)

Leonardo’s sketch for a bridge to span the Golden Horn (“Haliç”), seen from above and from water level. His notes in “mirror script” are clearly for his own use. (Institut de France, Paris)

Leonardo’s sketches for the bridge are found in Manuscript L, a small Codex stored in the Institut de France, Paris, a distance of 2300 km (1400 miles) from Istanbul. A bird’s eye view of the bridge shows the ends flared outward, in the manner of a swallow’s tail. Just below the bird’s eye view drawing appears the graceful silhouette of the bridge, the smooth curve of its runway set atop a parabolic arch, a masterpiece combining form and function! The specs are given in units of braccia, where 1 braccia=0.61 m or 2.1 ft. The bridge is meant to span the 400 braccia (240 m or 800 ft) wide Golden Horn, with its parabolic arch rising to 70 braccia (43 m or 146 ft) above the water. Its runway is smoothly extended to a length of 600 braccia (366 m or 1200 ft) on facing shores; and is tapered in its width at its peak to 40 braccia (24 m or 80 ft). The mathematics for the parabolic support for a bridge would not be worked out as a structural engineering problem until the 19th century, but Leonardo appears to have intuitively realized that this shape provided an especially strong support for the bridge.

In an inventory of its holdings published in 1938 the Topkapi lists the letter as E-6184. The official/scribe identifies the author as “Ricardo ‘the kafir’ of Genoa (the year of the letter is not given.) The word “kafir,” describes an unbeliever, an infidel. It is ironic that the official gets both the name and the city wrong. The letter, in fact, had arrived on a ship sailing from Genoa, possibly causing the confusion in the attribution. It was not until 1952 that the German scholar von Franz Babingen unequivocally established the connection between the letter in the Topkapi Archives and the drawing in the Institut de France.

Leonardo fails to secure an appointment to the court, never gets to see Constantinople, the Bosporus or the Golden Horn, or to offer precise specs for the bridge based on his own measurements.

In this satellite photo of the Bosporus Istanbul is seen as the city straddling two continents, Europe on the West and Asia on the East. The straits connect the Black Sea in the North with the Sea of Marmara in the South. And farther South still lie the Dardanelles and the Mediterranean. The Golden Horn is the estuary seen at the Southern opening to the Bosporus. Leonardo, the consummate scientist-engineer, would have been fascinated with the technology that allows us this view from hundreds of kilometers above the earth.

The Golden Horn, or Haliç to Turks, is an inlet, an estuary on the European side of the Bosporus measuring 10 km or 6 miles in length and 240 m (800 ft) in width at its entrance. It’s direction is East-West. The first bridge to span the Golden Horn was created in 1845 and lasted approximately 18 years. In distinction to the Golden Horn, the Bosporus measures 30 km (18 miles) in length and 3.329 km (2.1 miles) in width at the northern entrance and 2.8 km (1.74 mi) at the southern entrance. The direction is North-South. Thus the fourth project in the letter, a suspension bridge over the Bosporus, would have been entirely impractical in a time before high tensile steel cables could be produced in the 20th century. At its widest point the straits measure 3.4 km (2.1 miles) and even at its narrowest, 700 m (2300 ft). A pair of suspension bridges were built in 1973 and 1988, respectively.  A third bridge is presently under construction, and so is a tunnel below the Bosporus near its Southern opening.

Next: Part 3. “Vebjørn Sand and Variations on a theme of Leonardo”

The visionary Norwegian artist Vebjorn Sand resurrected Leonardo’s idea in his design of a bridge over Highway 18 joining Oslo and Bergen. Overcoming local political resistance, Mr. Sand spearheaded the construction of a pedestrian and bicycle bridge. His bridge, scaled down to approximately 25-30% of the size planned for the Golden Horn by Leonardo, was opened in 2001 in Ås. The next installment in this series will explore, “Vebjørn Sand and Variations on a theme of Leonardo”

Bulent Atalay, a scientist, artist and author, has been described by NPR, PBS and the Washington Post as a “Modern Renaissance Man.” He is the author of two successful books on the intersection of art, science and mathematics, with Leonardo, the pre-eminent Renaissance man, serving as the foil. His best selling book, "Math and the Mona Lisa," (Smithsonian Books, 2004) has appeared in 13 languages. Professor Atalay's academic background is in theoretical physics. He travels around the world lecturing at academic institutions and on cruise ships on the "A-subjects," art, archaeology, astrophysics, atomic physics and Ataturk, confessing that he knows much less about the "B-subjects," business, banking, biology and botany... He is the President of the Ataturk Society of America (ASA), dedicated to promoting Ataturk's ideals of science and reason over dogma and superstition, of a secular state with full equality of genders. For more details click on Bulent Atalay
  • Melinda Iverson

    I am so grateful, Professor Atalay, for your wonderful writing and the further details you add about LvD’s letter to the Sultan. I didn’t realize he included another proposal to span the Bosphorus!! I have only seen the first part translated, I guess. Fascinating. Very exciting to include Vebjorn Sand’s work in your next installment and how the bridge design has struck a resonant chord with our contemporaries. Thank you.

    • Hello Melinda, It is I who have to thank you for the use of photos. In the DVD I watched of Vebjørn’s interview for the Tourism Bureau in Turkey, Vebjørn expresses how utterly awe struck he was by seeing that initial exhibition. Do you have any idea where he saw it? Manuscript L, owned by Institut de France, allows the exhibition of the codex in different venues. The more we examine and understand Leonardo, the more we become use to basking in his reflected glory.

  • John Maenhout

    Dear Bulent,
    Again I read so much about Leonardo that is new to me — about the windmill. He must have had understood the windmill intuitively, and to think, that he thought of a hydraulic system to develop to empty water from boats (bilge pump). I learned about Istanbul as a natural bridge between Europe and Asia in school. What a great idea to build a bridge over the Bosphorus, a place where two continents come together. A Turkish friend wants to show me the Bosphorus, but I’m too old for this much travel.

  • Roderick

    Dear Bulent Atalay, Thank you for sharing these incredible stories with us, It’s truly interesting and exciting to learn more about the master Leonardo Da Vinci. Keep the stories coming.

    Kind regards,

    • Thank you for the gracious note. It is extraordinary that 500 years after he lived, we are still awestruck with Leonardo. He personally thought he was a failure, asking his assistant just before he died, “Did anything get done.” We must ask, were there a dozen different geniuses all using the same name.

  • does breast actives work

    Hey there! I’ve been following your web site for a long time now and finally got the courage to go ahead and give you a shout out from Kingwood Texas! Just wanted to tell you keep up the great work!

  • does breast actives work

    Hmm it appears like your blog ate my first comment (it was extremely long) so I guess I’ll just sum it up what I submitted and say, I’m thoroughly enjoying your blog. I as well am an aspiring blog blogger but I’m still new to everything. Do you have any tips for inexperienced blog writers? I’d certainly appreciate it.

  • harrison

    I became very pleased to discover this web-site.I wanted to good time for this wonderful read!! My partner and I are definitely savoring every bit of it and i also have you book-marked to check out blogs to your articles.

  • joel

    Prachtvolle Fragen, Sie haben gerade ein Emblem gewonnen.

About the Blog

Researchers, conservationists, and others share stories, insights and ideas about Our Changing Planet, Wildlife & Wild Spaces, and The Human Journey. More than 50,000 comments have been added to 10,000 posts. Explore the list alongside to dive deeper into some of the most popular categories of the National Geographic Society’s conversation platform Voices.

Opinions are those of the blogger and/or the blogger’s organization, and not necessarily those of the National Geographic Society. Posters of blogs and comments are required to observe National Geographic’s community rules and other terms of service.

Voices director: David Braun (

Social Media