India has the wettest place on Earth: Mawsynram in Meghalaya and it is home to some of the best bridges of the world. Comprising of living bridges that are formed as a result of the locals training the rubber trees to grow in a manner such that they form natural bridges, they have proven to be stronger than the bridges built by man. As the years pass, the bridges are only growing sturdy and are self-strengthening.
In a recent collection by Amos Chapple, a popular photographer, there can be images seen of people crossing the bridges that have been in place since years. You will be able to notice that the school children walk on the bridges as if it were their original path. There is a process involved in which the rubber trees and ladders formation is facilitated by tying knots tightly, while it is humid due to the rains.
The framework of the bridge is due to bamboo and the rubber trees get fixated to the structure one strand after the other. Eventually, before the bamboo gets rotten, the roots of tree easily start bearing the weight of an individual.