Question: why is the poem ozymandias set in a vague antique land?
Answer: The ancienct land might refer to Egypt because the ruins that he finds are of Ozymandias who was a pharaoh in ancient Egyptian times. Ozymandias was another name for Rameses II, the great pharaoh of Egypt. The poem speaks to the ruler who built a colossal statue of himself and placed it on a pedestal.