From Souvenir of Cork & Killarney: with 19 illustrations, complete with letterpress. Dublin and Belfast: Eason & Son Ltd., (n.d.)
Extract from the above publication:
"Blackrock Castle, built by Lord Mountjoy as one of the defences of Cork in 1604, and rebuilt in 1830, stands on the promontory of Ringmahon. William Penn, the founder of Pennsylvania, embarked from here for America. The castle is now used as a boathouse."
View a drawing of Blackrock Castle.