UNESCO and the Government of Sikkim are documenting Ru-Soam engineering, the traditional bridge-building knowledge of the Lepcha community. Ru-Soam refers to footbridges made of bamboo and cane in the Khangchendzonga Biosphere Reserve. Built without steel or concrete, they work much like modern suspension bridges. Their main parts are the support cables (Soamgyang), suspender loops (Ahool) and the bamboo deck (Soamgur). The bridges can span up to 100 metres and usually carry two or three people at a time. Being flexible, they withstand earthquakes well and leave a low carbon footprint.