In the Northeastern state of Meghalaya, India, there is an indigenous ethnic group of people known as the Khasis who have a very unique skill. They train the aerial roots of the Ficus elastica or the rubber fig tree, a type of banyan tree, into living root bridges across rivers. It is not known exactly when or how this tradition started, but the earliest record by a Lieutenant H. Yule is found in the 1844 Journal of the Asiatic Society of Bengal. In a place with incessant rainfall which rots away wood or bamboo bridges and rusts the metal ones, these bridges offer long-lasting means to cross the streams. The oldest bridge is believed to be 500 years old and the longest, located near the town of Pynursla, is over 50 meters long. These bridges naturally self-renew as they keep growing thicker and stronger as long as the tree remains healthy.
(For more on these living root bridges visit: http://mrbublenews.com/index.php/2018/04/19/the-living-root-bridges-of-cherrapunji-that-are-over-500-years-old/)