This robot was designed over 500 years ago, and it works

A knight in armor that sat up, waved its arms and turned its head, with nobody inside. Leonardo sketched it in the 1490s, and modern engineers who rebuilt it found that the idea holds up.

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Picture Milan in the 1490s. The city is ruled by Duke Ludovico Sforza, and his court loves a show: music, costumes, fireworks, surprises. Working for him is a painter and engineer in his early forties who fills notebook after notebook with ideas, from flying machines like his famous ornithopter to water pumps and stage tricks. His name is Leonardo da Vinci, and around 1495, according to most historians, he sketched something that sounds like science fiction: a mechanical man.

It looked like a knight in a full suit of armor. Inside there was no person, only wood, metal parts, leather, pulleys and cables. Pull the right strings and the knight would move by itself.

That was more than 530 years ago. To put that in everyday terms, it is roughly twenty generations of grandparents stacked one after another. And yet the machine is surprisingly close to how some robots are built today.

What could it do? Sources agree on the basics. Roboticist Mark Rosheim, who studied it for years, describes a knight that sat up, opened and closed its arms, moved its head on a flexible neck and raised its visor. Several other accounts also mention a jaw that could open and close, so the knight may even have looked like it was talking.

Why build such a thing? Nobody left a note saying exactly. The most common explanation is entertainment. The Sforza court in Milan held lavish parties, and a knight that suddenly came to life in front of guests would have been the ultimate party trick. A 2015 study summarized on Medievalists.net suggests it was meant to surprise and maybe even unsettle the duke's visitors.

Was it ever actually built back then? Here the honest answer is: we don't know. Some writers say Leonardo probably made a working version for the court. Others say it survives only as sketches. No original knight has ever been found, and no eyewitness report of it in action is known.

This is where the story gets personal. Leonardo was obsessed with how bodies move. He studied the Vitruvian Man idea of perfect human proportions, and later he drew muscles, bones and tendons in amazing detail, partly from real dissections.

He noticed that a body works a bit like a machine. Muscles pull on tendons, tendons pull on bones, and bones swing around joints like hinges. So what if you replaced the muscles with cables and the joints with metal pivots? According to historians who have studied the knight, that is roughly what he did. His robot was, in a way, an anatomy lesson you could watch move.

Why does this matter to you? Because it is the same logic engineers still use. Many robot arms and hands today are moved by cables or pistons that act like tendons. Leonardo got there with wood and rope.

Imagine a puppet, but with the strings hidden inside the body instead of held from above.

The knight's upper body had its own small controller in the chest. Turning it moved a set of gears, including a worm gear, the kind of screw-shaped gear you find in a guitar tuning peg. That drove the arms, so both arms could move together in a smooth, repeating motion. The legs worked with a separate crank and cables attached at the ankles, knees and hips.

In other words, the knight was not "thinking." It followed a fixed set of movements, a bit like a music box plays the same tune every time you wind it. That is still a robot in the engineering sense: a machine that performs a set of motions on its own once started.

Here is the strange part. For about four and a half centuries, almost nobody knew the knight existed.

Leonardo did not leave one neat blueprint. The drawings were scattered as small fragments across his notebooks, mostly in a giant collection now called the Codex Atlanticus, kept in Milan. Mixed in with thousands of other sketches, a few gears and pulleys don't exactly scream "robot."

Then, in the 1950s, the Italian scholar Carlo Pedretti spotted them. Several sources date his find to 1957. That is roughly 460 years after Leonardo drew them, nearly twice as long as the United States has existed. Pedretti realized the scattered pieces belonged together, and he later called it the first articulated humanoid robot in the history of Western civilization. That is his claim, and it is limited to the West for a good reason, which we will get to.

Knowing it existed was one thing. Proving it worked was another. That job fell to American roboticist Mark Rosheim, working with Pedretti's research. In 2002, for a BBC documentary, Rosheim built a working version based on Leonardo's sketches, according to a summary of its history on Reference.org. It moved. Five centuries of silence, and the design still did its job.

Rosheim's story did not stop there. According to LeonardoDaVinci.net, ideas he took from Leonardo's machines fed into robot designs he later created for NASA. So a sketch drawn for a party in Renaissance Milan ended up inspiring machines meant for space.

In 2007, Mario Taddei at the Leonardo3 center in Milan built another working version, using additional details from Leonardo's drawings. Two different teams, two working knights.

It is tempting to call Leonardo's knight "the first robot." It wasn't.

Around the 1st century, Hero of Alexandria in Egypt described moving figures driven by weights, ropes and water. In 1206, the engineer Ismail al-Jazari finished a famous book of machines that includes automatic musicians and servant figures. So people had been building moving mechanical figures long before Leonardo.

What makes the knight special is how closely it copied a human body: a sitting, reaching, head-turning figure built from a painter's study of real anatomy. That is why Pedretti said "Western civilization," not "the world."

The knight was not a one-off. Leonardo also designed a self-propelled cart, drawn in the Codex Atlanticus around 1478 to 1485 and powered by springs, like a wind-up toy. It could only roll a few meters, about the length of a living room, and was probably meant for stage shows. Some researchers describe it as programmable, because its route could be set in advance.

Then there was the lion. Around 1515, Leonardo made a mechanical lion for the new French king, Francis I. Old accounts say it walked forward, stopped and opened its chest to reveal lilies, the symbol of France. Historians disagree on exactly where and when it was first shown, and we mostly know about it from later writers, not from a surviving machine. Still, it was a diplomatic gift that literally walked into the room.

You might think that after 500 years, everything in Leonardo's notes would have been found. Not even close.

After Leonardo died in 1519, his papers were split up. In the late 1500s, the sculptor Pompeo Leoni cut many pages apart and glued them into new albums, separating art from science. The Codex Atlanticus alone has 1,119 sheets. If you read one sheet a day, you would need about three years.

Only this June, Florence's Museo Galileo launched a project called Leonardotheka that digitally reunites the Codex Atlanticus with about 550 Leonardo pages held in Britain's Royal Collection, as Artnet News reported. Researchers matched at least 50 torn pages back together using paper size, watermarks and ink.

And discoveries keep popping up. In early 2023, Caltech engineers announced that sketches in another notebook, the Codex Arundel, show Leonardo testing gravity with falling sand. His estimate was about 97 percent accurate, like scoring 97 out of 100 on a test, long before Galileo and Newton worked out the rules of falling objects.

The robot knight was sitting in plain sight for over 400 years, broken into pieces nobody recognized. Now that his notebooks are being stitched back together and searched by computer, it is fair to ask: how many more machines are still hiding in those margins, waiting for the right person to notice a few gears and a pulley? And which one will be next?