"Dublin bay" is defined by land masses in the shape of a large C, forming an immense "ring of bay and skyline." At the extreme northeastern reach of this arc lies the large, high, and wild peninsula called Howth Head (pronounced "Hoath"). Off the southeastern tip of the C, perhaps six miles away from Howth as the gull flies, lies small Dalkey Island and the rocks around it.
The third chapter of Ulysses shows Stephen walking toward Dublin along Sandymount Strand, on the large tidal flat that appears submerged in the photograph. Chapters 4-18 take place in Dublin, where the River Liffey flows into the bay at the center of the C. At the end of the last chapter Molly is recalling the day that Bloom proposed marriage to her on Howth Head. Thus the book begins at one end of the C, moves into the middle, and finishes at the other end.