Olympic torch: Relay visits Dublin and Belfast on day 19
The Olympic flame crossed the Irish border to be greeted by thousands in Dublin on Wednesday, before travelling north to Belfast.
Locog Chairman Sebastian Coe said of the torch's visit to Dublin: "The welcome has been extraordinary."
The flame left Northern Ireland in a ceremony at the border involving boxers Wayne McCullough and Michael Carruth.
The flame progressed north through Newry and Lisburn before returning to Belfast shortly before 17:00 BST.
Thousands of people turned out for the evening celebration outside City Hall which featured rock group General Fiasco, dance act Twist and Pulse and the City of Belfast School of Music Junior Choir.
Referring to the Dublin leg of the relay, Lord Coe said: "The crowds have been 10, 15, 20 people deep, they're hanging out of office windows, and I saw somebody halfway up a lamppost.
"I'm really pleased we came here. I felt it was a right thing to do.
"This is a country that's excellent at sport. You've got an extraordinary history in sport and having Michael Carruth run with it this morning symbolises what it's all about."
Carruth and long-time friend McCullogh were team-mates representing Ireland at the 1992 Olympics in Barcelona where McCullough, from County Antrim, took silver in the bantamweight division and Carruth, from Dublin, won gold at welterweight.
The handover of the flame took place at the site of the former customs station on the old Dublin road, south of Newry. Schoolchildren from both sides of the Irish border were there with their parents to witness the occasion.
McCullough said: "It was like going into the Olympic final again, you get emotional.
"This was something I was looking forward to all week, to do something cross-community and meet my good buddy Michael Carruth. I am honoured to be doing it."
The torch started its morning in Dublin with a "skywalk" over a glass section of the new roof at Croke Park stadium, carried by hurling player Henry Shefflin.
It wound its way around the Irish capital and later headed back across the border towards Belfast.
The trip to the Republic of Ireland capital recognises the "unique and deep ties" between Ireland and the UK, Olympics Minister Jeremy Hunt said.
Northern Ireland Culture Minister Caral Ni Chuilín described the torch's visit to Dublin as "significant" and said the torch had been really warmly received throughout the course of its journey in Northern Ireland.
She also paid tribute to those who had carried it: "A lot of the torch bearers are ordinary people who have done extraordinary things.
"They're carrying the torch not just as an international symbol of hope, vision and inspiration but also for overcoming their own personal difficulties."
Irish president Michael D Higgins greeted the flame in Howth, Dublin, and a host of sports stars were carrying the flame on its 125-mile journey.
They included former footballer Paul McGrath, ex-rugby internationals Denis Hickie and Shane Horgan and leading jockey Ruby Walsh .
Also among the torchbearers in Dublin were Anthony Sutherland, whose son Darren won a boxing bronze medal in Beijing in 2008, but was found hanged in his London flat the following year , and Bridget Taylor, the mother of Katie, who will be attempting to add a women's boxing gold medal in London to her four world championship wins.
A celebratory event was held at St Stephen's Green, where Sonia O'Sullivan, the former world and European champion and Olympic silver medal-winning runner, lit a special cauldron.
After running in the relay she said she had been "nearly as nervous" as before a race and it was a long 300m dash with the torch.
She said: "The Olympic torch has got a little bit of magic in it and I think you could see that in the crowds that turned out."
Pat Hickey, president of the Olympic Council of Ireland, said: "We will never have the Olympic Games in Dublin and the nearest we are ever going to come to it is the London Games, so to have the torch relay on our part of the island is quite unique and historical.
"We got a special derogation for it to move from Belfast to Dublin and we see the crossing of the border as a way of celebrating peace in Northern Ireland for the last 15 years."
At Croke Park, home of the Gaelic Games and headquarters of the Gaelic Athletic Association, Irish sportsman Sheflin, 33, paraded the flame along the rooftop before it began its journey through the city.
Henry plays hurling with his local club Ballyhale Shamrocks and has been a member of the Kilkenny senior inter-county team since 1999. He was the All-Ireland winning captain in 2007 and is regarded as one of the greatest players of all time.
He said carrying the torch was "up there with his eight All-Irelands (hurling medals)".
The Jedward twins, who have represented the Republic in the last two Eurovision Song Contests, took the torch to the post office in O'Connell Street and it was later met by Taoiseach Enda Kenny when it reached Leinster House, which was built in the 18th Century and has served as the national parliament building since 1922.
On Thursday , the relay takes in Newcastle, Dundrum, Clough, Downpatrick, Crossgar, Saintfield, Ballynahinch, Templepatrick, Antrim, Ballyronan, Magherafelt, Ballymena and Moorfields before leaving Northern Ireland for Scotland.
A total of 8,000 people will carry the flame during its 8,000 mile, 70-day journey to the opening ceremony of the Olympic Games in London on 27 July.