On Tuesday the Queen becomes the first British monarch to visit the Republic of Ireland.
Her Majesty is visiting at the invitation of President Mary McAleese who will formally welcome the sovereign at her official residence in Dublin, Aras an Uachtarain.
The president said the four-day tour was "an extraordinary moment in Irish history".
"(It's) a phenomenal sign and signal of the success of the peace process and absolutely the right moment for us to welcome onto Irish soil, Her Majesty the Queen," she added.
King George V, the Queen's grandfather, was the last reigning monarch to visit the country, in 1911, when what is now the Republic was then part of the UK.
The Irish government has mounted a huge security operation,to make sure the visit passes without incident.
Around 8,000 gardai or national police officers, and 2,000 soldiers are involved.
Meanwhile, the Irish army reported finding a bomb on a bus bound for Dublin.