The traveler has been to a barren desert where there is a ruined statue.

The traveler tells the narrator of the poem about the legs of the statue that stand in the desert. Then the face of it lies on the sand. There's a commanding look on the face of the statue; the sneer survives even though it has crumbled into the sand. There's a plaque that reads:

My name is Ozymandias, King of Kings;

Look on my Works, ye Mighty, and despair!

It's an interesting point for you to analyze the role of the traveller in Shelley's poem.  There are many personas to analyze in the poem, but the traveller is an interesting one because it is this figure who is able to relay the story of Ozymandias.  The world or land that the traveller describes is one that is barren or desolate.  It is almost as if the land that the traveller describes is empty, once being populated, but now is not.  Notice the language used to describe this such as the actual term of "desert" and the idea of "sand."  The only sign of what once might have been life is the decrepit statue that is described as "vast" and containing a "shattered visage."  This indicates to us that what once was is now empty, containing only this broken statue.  After the traveller describes the statue and the engraving, the closing couplet furthers the imagery of desolation in this setting with the idea of "lone and level sands stretch far away."  The land described is one of emptiness, only containing what is a cautionary tale for others.