The Republic of Ireland gave up its territorial claim to NI
In the referendum that followed the Good Friday Agreement, the Republic of Ireland voted by more than 90% to give up its territorial claim to Northern Ireland in exchange for north-south bodies.
BBC NI's Dublin correspondent Shane Harrison asks if the two parts of the island have become closer since then.
Motorists find it increasingly hard to tell where exactly the border is, with roads and motorways seamlessly linking one jurisdiction with the other.
But equally, it's easy to argue that over the last 10 years the Republic and Northern Ireland have grown miles apart.
That's because the Republic has become more self-consciously European, with the changeover to kilometres.
Since the middle of 2004, new cars south of the border no longer have miles indicators on their speedometer.
Many argue that the introduction of the euro, massive immigration to an (at least until recently) booming Celtic Tiger economy and a growing lack of media interest in what is happening in the other jurisdiction have accelerated a moving apart.
Eamon Delaney, a former Irish diplomat, and the editor of the current affairs magazine, Magill, subscribes to that view.
He says: "There are many factors, nothing to do with politics necessarily: the Celtic Tiger, the multi-cultural globalised nature of the south means it has drifted apart from Northern Ireland."
Mr Ahern denies there has been a political disengagement
The Irish minister for Foreign Affairs, Dermot Ahern, a border TD, denies there has been a political disengagement.
He points to good relations on the north-south ministerial council, business moving north across the border and his government's commitment to give Northern Ireland more than half a billion euros for infrastructure projects in the coming years.
But, he says, he understands why people in the Republic may be disappointed with the impact of the north-south bodies that replaced Articles 2 and 3 of the constitution which laid claim to Northern Ireland.
"The cross-border bodies have been, to a certain extent, hamstrung by the fact that the institutions were in suspension," he says.
"I think now that you have the full working institutions, it will allow the north-south bodies to move on in even greater store."
Sinn Féin's Dáil Leader, Caoimhghin O'Caolain, is one of those who believes the performance of the north-south bodies has been disappointing - partly, he says, because there isn't enough of them and partly because they don't appear to impact on daily lives.
He makes little secret of the fact that republicans now believe the road to their long cherished united Ireland is through an all-Ireland economy.
"We have clearly to accept the logic that a single island economy that would be to the benefit of all people on the island of Ireland can only best be served through one single administration on the island of Ireland that cherishes all its children equally."
Dublin was the centre of the Republic's economic boom
Dr Garret Fitzgerald was taoiseach at the time of the Anglo-Irish Agreement that first gave the Republic a say in Northern Ireland's affairs.
Decades of violence, resulting in massive subsidies from London and the failure by unionists in the Good Friday Agreement to negotiate a similar corporation tax rate as the Republic, and their unwillingness to have one industrial development body for the island, means the two parts of Ireland have grown further apart economically, he says.
And that, he argues, makes Irish political union even more remote.
Without the subsidies, he says, "Northern Ireland would be 20% worse off which means that even the most ardent Sinn Féin supporter vote against it or, alternatively, we'd have to increase our burden of taxation by a quarter, which isn't going to happen."
Ten years after the Good Friday Agreement, Ireland is still on a journey.
Relations between north and south are certainly much better, even though no-one can be certain whether the road ends with Irish unity, a stronger union with Britain or somewhere in between.