Leonardo Da Vinci self supporting Bridge
Leonardo da Vinci's Ingenious Design for a Self-Supporting Bridge

Of the many structures Leonardo da Vinci designed, perhaps none made more ingenious use of materials than his practical design for an easy-to-assemble, self-supporting bridge.

Leonardo self supporting bridge was designed while he was under the patronage of Cesare Borgia. Borgia employed Leonardo as his military engineer, in turn, Leonardo would design and build magnificent machines of war. One such machine was this bridge. Its simplicity and genius cannot be underestimated.
Why was the self supporting bridge needed
It requires no specific skills to manufacture the parts, apart from a few men that are handy with an axe ,It can also be carried by a handful of men into any battlefield. It requires no nails or ropes to hold it together – the bridge is self-supporting and would be capable of holding a substantial amount of weight.
Here’s a father and son demonstrating its construction in their backyard, without using a single tool:
With a series of wooden poles and beams, “Stick-Boy” shows his Dad how to build Leonardo da Vinci‘s self-supporting arch bridge, also known as the emergency bridge. No nails, screws, rope, glues, notches, or other fasteners are holding the bridge in place… just friction and gravity.

The design is not limited to just the five crossmembers depicted above. Here’s one with nine crossmembers, erected as decoration in the German city of Freiburg:

You might be wondering how strong the design is. Well, here’s a version erected out of construction lumber in Stuttgart, Germany, with the city’s Mayor being driven across it:
That was at an event last year celebrating traditional carpentry. (The folks you see wearing black hats and vests have donned traditional German builders’ garb.) Incredibly, the 10-meter-span structure was assembled by eight apprentices and two masters in about ten minutes! Here’s how they did it: