Most bridges are built to stay in place, enhancing their durability and ensuring they help people tackle challenging terrains. Drawbridges are an exception, with some disconnecting at the midsection and folding upward to allow boats through, and others rotating 90º to let boats pass on either side.
On the other hand, a pedestrian bridge located in London is getting quite a bit of attention because of its non-traditional method of folding up into a ball when not in use.
It's possible for the bridge to wrap in this manner because it's composed of several carefully measured trapezoidal sections with just the right angles. Hydraulic-powered pistons on each section of the bridge carefully extend and retract the bridge when someone needs to cross while packing it away when not in use.
Despite what looks like a bit of a questionable design, the bridge can reportedly support up to 20,000 pounds.
