In the wettest place in the world, people don't cross bridges that were built. They cross bridges that were grown.
In the depths of northeastern India, within sight of the India-Bangladesh border, in one of the wettest places on earth, bridges aren’t built, they’re grown. The southern Khasi and Jaintia hills are humid and warm, crisscrossed by swift-flowing rivers and mountain streams. On the slopes of these hills, a species of Indian rubber tree with an incredibly strong root system thrives and flourishes.
The Ficus elastica produces a series of secondary roots from higher up its trunk and can comfortably perch atop huge boulders along the riverbanks, or even in the middle of the rivers themselves. The War-Khasis and War-Jaintias, two closely related tribes in Meghalaya, long ago noticed this tree and saw in its powerful roots an opportunity to easily cross the area’s many rivers. Now, whenever and wherever the need arises, they simply grow their bridges.
In order to make a rubber tree’s roots grow in the right direction—say, over a river—the people of southern Meghalaya have used several different strategies. Sometimes, the roots of the trees are simply pulled, tied, twisted, and encouraged by hand to merge with each other, until, over time, they form the desired architectural structure. Root bridges have also been made by creating scaffolds out of wood and bamboo, and then training the young roots out across these temporary structures, replacing the more perishable elements many times as they rot in the intense monsoon seasons.