Not really a tapestry, but a piece of linen with embroidery over 200 feet long and 2 feet high.
It depicts William the Conqueror's defeat of Harold, which led to the Norman conquest of England.
It is likely that it was commissioned by Bishop Odo, William's half-brother, and made in England in the 1070s. In 1729 the hanging was rediscovered by scholars when it was being displayed annually in Bayeux Cathedral.
For more information on the tapestry, see http://en.wikipedia.org/wiki/Bayeux_Tapestry
OK, you cannot take photos of the tapestry, so this is my photo of a postcard.