In the first visit by a British monarch to the Republic of Ireland, the Queen has laid a wreath at a memorial to those who fought for Irish independence.
The ceremony took place at Dublin's Garden of Remembrance, Ireland's monument to its fallen heros, before a hushed crowd of dignitaries, soldiers.
The Queen's visit to the Republic is the first by a British monarch since Ireland won independence in 1921.
One of the Republic's biggest ever security operations was in place for the visit.
Earlier, it emerged that a pipe bomb found on a passenger bus bound for Dublin had been made safe by an Irish army team.
Scuffles took place in the centre of Dublin and on streets near the remembrance garden between police and republicans protesting against the visit.
The sounds of protesters could be heard during the laying of the wreath and black balloons were released by some demonstrators, the BBC reports.
Because of security fears, the area around each royal stop were cleared of onlookers, leaving streets empty of the usual cheering crowds that greet the Queen elsewhere.
Following the wreath-laying the Queen went on to Trinity College to be shown the Book of Kells, an ancient illuminated manuscript in Latin, containing the four gospels of the New Testament.
The Queen and Duke of Edinburgh were then driven in a bombproof and bulletproof car to the official residence of the Irish president, where she and Prince Philip signed the visitors' book in the residence's lavish state ballroom.
King George V was the last reigning monarch to visit Ireland, in 1911, when what is now the Republic was part of the UK.
