The economic spin off from Londonderry's City of Culture year could reach £500 million, the council's chief executive has claimed.
Sharon O'Connor said the bonanza from the 1.3 million visitors expected to descend on Derry during 2013 would generate global exposure and jobs.
Ms O'Connor said: "The potential is just massive. We are estimating £500 million. The value is across a whole range of things.
"It is not necessarily just all money in tills - it is also about the media value of the exposure that we get and there's no doubt that jobs will be created."
Capital investment worth £100 million has already been pumped into Derry since the City of Culture title was secured in 2009.
The latest cash injection came earlier this year when Northern Ireland environment minister Alex Attwood pledged £100,000 to tackle dereliction and remove graffiti.
Officials have also estimated that up to £98 million in additional wages and profits could be generated over the next 12 months.
But there are other benefits which are more difficult to put a value on. The Culture Company which is organising next year's celebrations hope that by the end of 2013, Derry will have jumped from 49th to 20th in the league table of top UK cities.
Ms O'Connor also said the educational and social legacy was priceless. She added: "We are giving our young children an opportunity to see futures for themselves that in other circumstances they might never have been able to imagine.
"Bringing this global exposure to their city shows them that the opportunities for them are unlimited. And you can't put a value on that."