Like a practical flying car, there are some technological advances that have long been expected but never came to be. On the other end of the spectrum, there are inventions that were made way ahead of their times. Some became popular and led directly to modern technologies. Others ended up lost in antiquity until the world caught up and the ideas were revitalized centuries later.

Here’s a list of 10 inventions that were made earlier than you might expect.

1 Armored vehicles

In the 15th century in Italy, Leonardo da Vinci drew plans for an armored, fighting vehicle that could be considered a precursor to armored cars and tanks. It had a conical shape inspired by a turtle shell and an array of light cannons around its perimeter.

For movement, it relied on four strong men turning two large cranks. In the design, the gears were improperly located, so the vehicle would not work. Some believe this error was made deliberately by da Vinci in case his plans were stolen.

In 2010, a group of engineers fixed the design flaw and built a recreation of the vehicle. It was too large to move on rough terrain. It’s believed that da Vinci designed the vehicle to intimidate the enemy rather than be an effective fighting weapon.(1,2,3)

2 Analog computers

The Antikythera mechanism is a device dating from around the 2nd century BCE. It is a complex mechanism made up of at least 30 gears. It was used for calendar and astrological purposes.

It could predict astronomical positions on a particular date. Turning a hand crank changed the date and caused the machine to simultaneously calculate the position of the moon, sun, moon phase, eclipse, and calendar cycles. It may have also been capable of predicting the position of planets.

The technology behind the device was lost until astronomical clocks were developed in 14th century Europe. The Antikythera mechanism was discovered in 1900 inside an ancient Greek shipwreck. Museum staff overlooked the device for two years. At first glance, it appeared to be just a lump of corroded bronze and wood.(source)

3 Vending machines

Hero of Alexandria, who lived from 10 CE to 70 CE, is credited with many inventions.  One of them was the world’s first vending machine. It was a coin-operated machine for dispensing an allotted amount of holy water.

The invention helped temples to prevent worshipers taking more than their fair share. The inner mechanism of the machine was simple. When a coin was inserted in the slot, it would fall onto a lever. The weight of the coin pushed the lever down, which opened a valve. When the lever had tilted enough, the coin would slide off and the valve would close.

The idea of vending machines did not catch on for many years. The next major development came in the 1880s when the first commercial-grade vending machine was made for selling postcards.(1,2)

4 Automatic doors

Another of the many inventions of Hero of Alexandria is his idea for automatic doors. This invention was designed to open the doors of temples. It would allow priests to simply light a fire on an altar which would then set hidden mechanisms into motion, and the doors would seem to open on their own.

It involved using the heat from the fire to expand the air in a vessel. This heated air would create pressure that forced water into buckets. The buckets would act as weights to pull on ropes. The ropes would turn spindles to open the doors. Once the doors were open, the mechanism would blow compressed air through a trumpet as a finale to the spectacle.

When the fire was extinguished and the altar cooled, the mechanism would reverse. Water would automatically siphon out of the buckets and allow counterweights to close the doors.

There’s debate over whether Hero’s design was ever built. But the idea was way ahead of its time. It wasn’t until 1931 that the first model of an automatic-opening door was patented and put into use.(1,2)

5 Programmable robots

Hero of Alexandria is also credited with creating the first programmable robot. It was a wheeled cart powered by a falling weight. By winding a string around the axle in in different patterns, the cart could be “programmed” to follow a particular path.

The falling weight was attached to a string wound around the axle. There were pegs on the axle that allowed the string to be wound in different ways to control turning, forward movement, and reverse. The cart was used in the theater to carry other automated spectacles around the stage. Hero once created a mechanical play that included automated actors that danced and poured wine.(1,2,3)

6 Heat ray weapons

Ancient Greek historians recorded that Archimedes created a heat ray that burnt enemy ships during the Siege of Syracuse in 214-212 BCE. It involved using mirrors arranged on the shore to focus sunlight on a single point.

There has been debate over whether the story is credible. A number of tests have been carried out in an attempt recreate the event, including two tests in 2005 by M.I.T. students. These tests suggested the story was possible, although the weapon would be extremely sensitive to cloud cover and would require the ships to be very close. MythBusters also conducted two experiments and concluded that the mirrors would be more effective at simply blinding or distracting the crew of a ship.

Another idea for a heat ray weapon was developed during World War II by German scientists. They made plans for creating a “sun gun.” It involved using a reflector with an area of 3.5 square miles attached to a space station. They calculated that it could focus enough heat to burn a city or make an ocean boil.

Heat ray weapons are still being developed. In the early 2000s, the US military created the Active Denial System (ADS). It is a non-lethal weapon designed for crowd control and security purposes. It works similar to microwave ovens by sending out wave energy that excites the water and fat molecules in the human skin, instantly heating them. It reportedly made test subjects feel like their skin was on fire. The weapon was deployed to Afghanistan in 2010 but was never used. It was recalled back to the US about one month later. Critics have speculated that it could be made ineffective by heavy clothing or environmental conditions.(1,2,3,4)

7 Rapid, long-distance communication

In 1792, France had a network of 556 semaphore towers that enabled communication across the country.

Humans have communicated over long distances since early history. Ancient cultures used torches and smoke signals. But the idea of sending optical messages was refined with the semaphore telegraph. The idea behind it was conceived in the 1600s.

It involves using a series of towers with pivoting shutters that can be arranged to create symbols. Each tower passes the message to the next tower in the line. France developed a network of semaphore lines stretching 3,000 miles. The network was developed for war efforts. It provided intelligence to the central government and allowed them to transmit orders. When compared to post riders, the other option for long distance communication at the time, semaphore lines were much faster. This type of communication system remained popular even after the invention of the electric telegraph in the 1830s. It wasn’t until 1846 that the French government started replacing its semaphores with electric telegraphs. While electric telegraphs offered the benefits of being faster and keeping messages private, some critics saw telegraph lines as having one major weakness: “They are so easy to cut.”(1,2)

8 Psychological warfare

While leading the Mongolian Empire in the 13th century, Genghis Khan created some innovative forms of psychological warfare. They included using arrows that were designed to whistle as a scare tactic.

The earliest forms of psychological warfare were simple. When two armies were about to face off, they would shout and make noises designed to intimidate the opponent. Genghis Khan was one of the first leaders to use more advanced forms of psychological warfare.

For instance, Khan used a number of tricks to make his army seem larger than it really was. They included tying objects the tails of the army’s horses so they stirred up a large cloud of dust. In addition, he ordered every soldier to light three torches at night.

Also, Khan used some unusual tactics designed to frighten the enemy.  For instance, his soldiers used arrows that were specially notched to create a terrifying whistling noise as they flew through the air. That tactic was mirrored by the German military in WWII when they outfitted dive bombers with wailing sirens for intimidation purposes.(1,2)

9 Cruise missiles

The “Kettering Bug,” is an unmanned aircraft that is the predecessor to cruise missiles. It was developed by the US military and its first flight was in 1918.

The US Army Aircraft Board asked Charles Kettering to create a flying bomb that could hit a target 64 kilometers away. Orville Wright worked on the project as a consultant. They designed an unmanned plane with wings made of cardboard and a fuselage made from wood laminates and paper-mâché. It used a gyroscope to help guide it in the direction of the target.

In order to get the “Bug” to hit the ground when it reached its destination, technicians would calculate the number of engine revolutions needed to reach the target. When an onboard counter reached that preset amount, the engine was shut off and bolts attaching the wings were retracted. The wings would fall off, and the “Bug” would fall onto the target. It carried a payload of 180 pounds of explosives. There were some successes in the initial testing, and 45 were produced by the end of the war. But it was never used in the field out of fear of hitting friendly troops.(source)

10 Military submarines

The first successful submarine was built in 1620 in England. During a demonstration, it stayed submerged for three hours. It used ores for propulsion and had hoses attached to floats to provide fresh air to the crew. Almost 100 years later, in 1718, a Russian carpenter pitched his idea for the first military submarine to Tsar Peter the Great.

The design was like a giant barrel. The submarine would be armed with “fire tubes,” so it could approach an enemy boat, stick the tubes above the water’s surface, and spray the boat with a flammable mixture. It also incorporated an airlock so the crew could exit under water and destroy the bilges of ships. After a number of botched tests and the death of Peter the Great—the project’s main supporter—the idea was scrapped.

The next milestone in the development of military submarines came in 1776 when American David Bushnell designed the “Turtle.” It was egg-shaped and used hand-powered propellers. There’s some debate over whether the Turtle was ever used in battle. American reports say the Turtle was used in an attempt to attach a bomb to the hull of a British warship, but the mission was aborted when the British spotted the submarine. Some historians say reports about the Turtle may have been American propaganda as there are no British records of the attempt, and the route the Turtle would have taken crosses a tidal stream that likely would have exhausted the operator.(1,2)