Red lght flickers on top of Poolbeg lighthouse with cruise ship sailing, Dublin Ireland

red lght flickers top poolbeg lighthouse cruise ship sailing dublin ireland poolbeg lighthouse great south wall south bull wall port of dublin aerial drone ringsend poolbeg peninsula dublin bay sea wall bull wall equidistant sea cliff historic structure octagonal stone staircase dublin port company comissioners of irish lights standard entrance port harbor architecture tourism nature landmark beacon nautical navigation light safety maritime marine