Seems like you can make just about anything out of recycled cardboard if you are clever enough!
Geek.com writes: "Kariv got inspired by the man who made a canoe out of cardboard, and combined his own passion for bicycles and recycling to create a functioning cardboard bicycle. It can withstand water, humidity, and is surprisingly strong. As the video above shows, it took quite a while to develop with Kariv working through several generations of the design. The bicycle needed to be strong enough to seat a person of up to 140 kilograms, which at first led to prototypes that were bulky and uncomfortable. But as with most things, the more you work on an idea, the better you become at using the materials to see it to fruition."