Old Chain-Bridge at Chaksam.
The Chakzam Bridge (also Chushul Chakzam) was a suspension bridge that spanned the Yarlung Tsangpo river near Lhasa in Tibet. When it was built at Jagsamka, in 1430 by Thang Tong Gyalpo (1385-1464), its main section was the longest unsupported span in the world, with a central span estimated at around 137 metres (150 yards). At the time it was built, there were no suspension bridges anywhere else in the world.
Diagram by an Indian spy working for the Survey of India in 1878