Thousands of people turned out in Dublin today to witness the demolition of the first of the famous Ballymun Towers.
A 120-tonne crane, which was imported from England, began knocking down balconies on the 15-storey Pearse Tower to great cheers.
As the sound of U2's Beautiful Day blasted out from portable speakers, the Taoiseach, Mr Ahern said it was the start of a new future for Ballymun.
He said he remembered when the towers were built in Ballymun in the late 60s and the social problems that had followed them.
"I know the day, for all the people here, is full with good thoughts and bad thoughts but it is all about moving forward."
It is expected to take four weeks for the first eleven storeys of Pearse Tower to be demolished, the last four storeys will be demolished with conventional demolition cranes.
The state-owned company spearheading the €2.5 billion redevelopment project, Ballymun Regeneration Limited, said there would be 8,500 tonnes of rubble from Pearse Tower alone.
BRL managing director Mr Ciaran Murray said: "It's the beginning of the end of the high-rise in Ballymun."
The thousands of locals who gathered to witness the start of demolition had mixed emotions. Mr Thomas Ward (34), who came with his nine-year-old son Thomas junior, said it was sad to see the tower going down. "I came here to see the history of Ballymun going. It's good for the kids growing up around the area. There's a lot more for them."
As part of the development project, new BRL has built a new swimming pool, a new civic centre, a community art centre and further facilities are on the way.
The two other tower blocks will be demolished in phase one of the programme, along with four-storey blocks and one eight-storey block. The former residents will be moved to new two, three and four-storey homes in Ballymun.
Director of the Ballymun Partnership, Mr Declan Dunne
Mr Paul King, a local painter and decorator from the nearby Poppintree area, said he was delighted to see the start of demolition. "I've been here in the 1980s when there was no work and half my mates were dead from drugs. There's a lot of positive stuff happening in Ballymun now," he said.
Mr Ahern signed autographs for local children before leaving to see the Dublin football team play Longford in the All-Ireland qualifier in Portlaoise.
Mr Declan Dunne, the director of the Ballymun Partnership, which provides community services to locals, said the ceremony was very moving. He said the demolition would reassure locals who had become frustrated with some of the delays in the redevelopment project: "To see a piece falling from the tower to the ground means that people can believe it's happening. People believe what they see with their own eyes."
Around 600 families have been rehoused in the new Ballymun dwelling and a further 902 homes are under construction. It is expected to take until at least 2012 until all the 20,000 people in Ballymun are relocated in new homes.