The harbour is the defining feature of the town and the reason it became important in the first place. Enclosed by the two great granite piers, it shelters a large marina, the ferry terminal for the Stena Line crossing to Holyhead, and the yacht clubs that have operated here since the early 19th century.
Walking either pier takes about 30 minutes each way. The harbour itself is active with sailing boats and the occasional large ferry, and the views from the pier heads back to the Wicklow Mountains to the south and the Hill of Howth to the north are some of the best in the area.