Much of Proteus takes place near "the south wall," one of two great seawalls that funnel the River Liffey into Dublin Bay through an area known by the name of Poolbeg. Partway along this wall sits an old hotel known as "the Pigeonhouse."
After walking along the Sandymount strand (the section of beach east of the suburb of Sandymount), Stephen turns first northeast toward the wall, and then east along it, walking beside its great "boulders" which he imagines as "piled stone mammoth skulls." Finding himself "nearer the edge of the sea" to the east, he decides that he has gone far enough and retraces his steps: "He lifted his feet up from the suck and turned back by the mole of boulders." One meaning of "mole," according to the OED, is "A massive structure, esp. of stone, serving as a pier or breakwater, or as a junction between two places separated by from each other by water."
Stephen's jaunt will conclude by watching the incoming tide from the rocks, climbing onto the wall, continuing west on the road that runs atop it, and walking back to solid land dry and safe: "The flood is following me. I can watch it flow past from here. Get back then by the Poolbeg road to the strand there."
Dublin's Great South Wall or South Bull Wall ("bull" is a synonym for strand or beach) was constructed of wood pilings and gravel in the early 18th century, and reinforced with huge granite blocks (quarried in Dalkey, and floated in by barges) in the second half of the century. At the time of its construction it was the longest seawall in the world. The purpose was to protect ships from violent weather in Dublin Bay, which often wrecked vessels in the sands of the estuary and, even when not so disastrous, could delay entry into Dublin for weeks.
A second seawall, the North Bull Wall, was built in the first half of the 19th century to solve the problem of silting at the mouth of the Liffey. Together with the south wall, which it angled down to nearly meet, it effectively scoured away silt and sand, deepening the river channel and allowing ships to proceed farther upstream.
At the end of Finnegans Wake, as Anna Livia drifts out to sea, she thinks of passing the juncture where the two long arms of seawall come nearly together: "sad and weary I go back to you, my cold father, my cold mad father, my cold mad feary father, till the near sight of the mere size of him, the moyles and moyles of it, moananoaning, makes me seasilt saltsick and I rush, my only, into your arms. I see them rising! Save me from those therrble prongs!" The 1902 map here illustrates how the two prongs come together to force the river's water out into the cold miles of open ocean.
Other features of the south wall figure in Ulysses. After construction of the wall was complete, a lighthouse was built at its far end. This lighthouse, painted a distinctive bright red, is mentioned in the novel as "the Poolbeg light." During the construction of the wall, a storehouse for materials was built on land created about halfway along its length. When the wall was finished, the caretaker who lived in this building, John Pidgeon, converted it into a tavern and later a hotel, to cater to sailors and travelers arriving in Dublin from long sea voyages. It became known as "the Pigeonhouse," and although the name has nothing to do with birds, it sets Stephen's mind tumbling through thoughts of pigeons and wild geese.
In 1798, fearing French invasion, the government took possession of the Pigeon House, turned the hotel into officers' quarters, and built a barracks and fortifications. In the 1866 print here, the distinctive shape of the Pigeon House can be seen to the left of the huge hulking fortifications. In 1897 the Dublin Corporation bought the land and buildings, demolished the fort, and constructed a coal-fired electricity generating station, which began producing power in 1903. That power plant was decommissioned in the early 1970s, replaced by a pair of much smaller smokestacks with red and white stripes at the top which can be seen in the largest of the photographs.
In the Dubliners story called "An Encounter," three boys plan a day of "miching," or truancy from school. "We arranged to go along the Wharf Road until we came to the ships, then to cross in the ferryboat and walk out to see the Pigeon House." They never get that far.
At the end of Cyclops, Bloom's departure from Barney Kiernan's pub is imagined as a maritime launch: "the mastodontic pleasureship slowly moved away saluted by a final floral tribute from the representatives of the fair sex who were present in large numbers while, as it proceeded down the river, escorted by a flotilla of barges, the flags of the Ballast office and Custom House were dipped in salute as were also those of the electrical power station at the Pigeonhouse and the Poolbeg Light."