The living root bridges of Cherrapunjee, India are made of real live rubber tree roots (Ficus elastica). Native people have developed a method of using the root systems of these massive trees to create beautiful “root bridges” which span rivers.
The ingenuity and time to create something of this magnitude are astronomical. The double bridge is thought to be some 500 years old.
“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. The bridges are alive and still growing and gain strength over time.” – Wikimedia
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via: http://www.atlasobscura.com/places/root-bridges-cherrapungee