A bridge is assembled from eight parts. Each part has a platform and a trapezium railing. The top of the adjacent railings are connected with two arms that are hinged to an extendable vertical bar. When the bars are extended the bridge curls up into an octahedral shape.[more]
Such a bridge, designed by Thomas Heatherwick, can be found in London. There the extendable bars are hydraulic rams.[less]
For more information on this bridge, see the Wikipedia entry.