Here are some images of Academy Hobby Model Kits Leonardo Da Vinci's Arch Bridge.
From the instructions"
The design uses a self supporting arch concept to distribute weight through the full curve of the arch.
The more weight the bridge carries, the stronger it becomes.
On the other hand, if one key component is removed, the bridge will fall.
It was originally intended as a quick build, wood bridge for use by the military.
Removing a single piece of wood while the enemy was crossing could cause the bridge to collapse drowning enemy forces.