The city of Cork will grow to nearly five times its size and increase its population by some 85,000 to 210,000 overnight as its historic boundary extension - the first since 1965 - takes effect at midnight.
City council chief executive, Ann Doherty, said it will mark a milestone in the city's journey towards becoming Ireland's fastest growing city.
"The historic expansion of the city allows the city council to plan for a city of sustainable urban growth and realise its potential as a city of scale and the fastest growing city in the country in the next 20 years," she said.
"Cork is a city of neighbourhoods and we want to strengthen that. But if we are to embrace the challenge of growing the city's population by another 120,000 by 2040, that does require us to ensure that we make the best use possible of land, and that has to be done in a sustainable way. The boundary extension will help that."
The Lord Mayor, Cllr Mick Finn, welcomed those living around Cork Airport, in Douglas, Rochestown, Ballincollig, Blarney and Glanmire into the city.
"We look forward to them bringing their expertise and experience with them," he said.
The head of the city's transition team, David Joyce, said the city has undertaken a massive internal restructuring on both an executive and political level.
New departments have been set up, including one focused on 'place-making' and another with 'climate change' at its core, council meetings have been re-arranged and a customer service unit has been set up to provide citizens with a one-stop-shop style point of contact with City Hall.
The city's director of strategic and economic development, Fearghal Reidy, said the extension will help reflect the ambition of the city, and insisted that people will be central to future planning.
"The people living in the extended areas already relate to the city. This is a real opportunity for them to participate stronger in terms of planning and development in the city that they live in," he said.
Mr Joyce said the city's commercial rate will actually reduce by a fraction of a percent to come into line with the county's slightly lower rate.
The extension of the city boundary marks the end of a long and at times controversial process in the wake of the 2015 statutory Smiddy report which recommended a merger of the city and county councils.
Over a dozen former Lords Mayor branded the merger proposal an attack on democracy and a potential disaster for the city. It triggered a High Court threat by the city.
That controversy led to the establishment of a review group which ultimately recommended a boundary extension.
When a compromise boundary couldn't be agreed, legislation was deemed necessary and signed into law earlier this year.
The extension in numbers:
the increase in population from 125,000 to 210,000
the area of the expanded city, a fivefold increase from 39km2
the number of electors who have moved from the county to the city
the number of staff who have moved from County Hall to City Hall
increase in the city's stock of social houses
the length of additional road network transferring to the city
the number of public lights being added to the city's existing inventory of 14,000
the number of libraries joining the city's existing network of seven
the number of cemeteries transferring to city control
the number of parks transferring
the number of playgrounds transferring