This living root bridge is made from the roots of the Ficus elastica or rubber wood tree. The tree produces a series of secondary thin, tender roots from higher up its trunk. In order to make a rubber tree's roots grow in the right direction, the Khasis use betel nut trunks, sliced down the middle and hollowed out, to create root-guidance systems and to prevent the roots from fanning out and make them grow straight out. When they reach the other side of the river, they're allowed to take root in the soil. Given enough time, a sturdy, living bridge is produced.
It takes ten to fifteen years to become fully functional, but they're extraordinarily strong - strong enough that some of them can support the weight of fifty or more people at a time. Because they are alive and still growing, the bridges actually gain strength over time. Some of the ancient root bridges used daily by the people of the villages around Cherrapunji may be well over five hundred years old.