Mentioned by Lonely Planet
Top 20 free things to do in Dublin
"On the Southside choose from Sandymount beach, Sandycove and Seapoint, popular with local sea swimmers. Seapoint is home to a Martello tower that's now the headquarters of the Genealogical Society of Ireland. On the Northside you have Dollymount beach, a 5-km long stretch set to the backdrop of Dublin's Poolbeg Chimneys and Howth Head, and is surrounded by the North Bull Island Nature Reserve."