††††We know that drawbridges were around from at least 2000 BC: an Egyptian fortress dating from about that time had a drawbridge which moved on rollers.
Drawbridges were initially used for defence reasons, but were later also used to allow tall ships to pass under them.
Modern drawbridges have one or two counterweighted deck members. These pivot upwards to allow ships to pass underneath. Such bridges are also called bascule bridges. One example is the double bascule bridge, Tower Bridge, in London which first opened in 1894.
