In one hilly area in the rainforest of northeastern India, they build bridges out of living trees. Specifically the roots.
The root bridges, some of which are over a hundred feet long, take 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. In fact, because they are alive and still growing, the bridges actually gain strength over time -- and some of the ancient root bridges used daily by the people of the villages around Cherrapunjee may be well over five hundred years old.