Japanese architect Shigeru Ban designed this "paper bridge" made out of cardboard tubes:
Built half a mile from the Pont du Gard -- a section of ancient Roman bridge classed as a UN World Heritage site -- Shigeru's cardboard-tube structure is strong enough to carry 20 people at a time. [...]
Weighing 7.5 tonnes, the bridge is made from 281 cardboard tubes, each 11.5 centimetres (four inches) across and 11.9 millimetres thick. The steps are recycled paper and plastic and the foundations wooden boxes
packed with sand.
http://www.france24.com/france24Public/en/news/culture/20070727-paper-bridge-japanese-shigeru-ban-french-river-gard.html - via Sensory Impact