The Giant's Causeway is one of Northern Ireland's most popular spots
The Northern Ireland Tourist Board (NITB) is to provide a £9.25m grant towards the building of a new Giant's Causeway visitors' centre.
The grant represents half the cost of the project which will serve Northern Ireland's most popular tourist site.
The Heritage Lottery Fund had already pledged £3m and the National Trust will invest £4m.
The National Trust is seeking to raise the remaining £2m from public donations which have so far reached £215,000.
The visitors' centre, due to be completed in 2012, was designed by Dublin architects Heneghan Peng, and will be hidden from the coastal landscape by a grass roof.
It will have environmental features such as water-permeable paving, natural lighting and rainwater harvesting.
The decision to go ahead with the centre follows years of controversy after the original visitors' centre burned down in 2000.
Alan Clarke, Chief Executive of NITB, said the project would help promote tourist destinations beyond the Causeway.
"This will provide opportunities to grow the tourism sector by signposting visitors to other attractions in the region, increasing the time that visitors stay in the region and increasing the amount spent by visitors."
An artist's impression of how the visitor centre may look
The National Trust's Director for Northern Ireland, Hilary McGrady, said work should begin on the site "by the end of spring".
"I am delighted that the Northern Ireland Tourist Board and the Department of Enterprise, Trade and Investment have continued to support this massive project and reflect their confidence in our ability to deliver," she added.
The Giant's Causeway's unique rock formations of rugged symmetrical columns have, for millions of years, stood as a natural rampart against the ferocity of Atlantic storms.
The 'discovery' of the causeway was announced in a paper to the Royal Society in 1693.
At that time, there was furious debate over whether the causeway had been created by men with picks and chisels, by nature, or by the efforts of a legendary giant.
Scientists now agree the naturally-formed patterns of rock were formed 65 million years ago by volcanic activity.