Lighthouse is the centerpiece of the story.  Light is knowledge and it’s construction was a wonder of its time.  What conflict faces the protagonist in this story?  It must emphasize the importance of physical life.  Does the protagonist believe that he will achieve the greatest knowledge (e.g. nirvana) in life after death?  What happens to the lighthouse when its architect is gone?  The lighthouse was built to support trade.  What happens to trade and commerce when Alexandria falls?