The Irony in Ozymandias

In the poem Ozymandias, Shelly describes a very proud and haughty king.  This king had, in his day made a great name for himself by building many great structures.  He also had a statue built of himself standing near his buildings.  Shelly says that a man once told him a story about seeing the remains of Ozymandias' statue which was two legs with the sneering head broken off and lying on the ground in the desert.  On the ground next to these was a plaque, it read as follows, "My name is Ozymandias, king of kings: look on my works ye mighty and despair."  Around the head and legs there was nothing else, no buildings.  Just a sandy desert for as far as the eye could see.