Norway is starting construction on a "doomsday vault" in the Arctic which is designed to house all known varieties of the world's crops.
The Arctic seed vault will be built into mountain rock
Dug into a frozen mountainside on the island of Svalbard, it is hoped the project will safeguard crop diversity in the event of a global catastrophe.
More than 100 countries have backed the vault, which will store seeds, packaged in foil, at sub-zero temperatures.
Prime Ministers from five nations helped lay the cornerstone on Monday.
Premiers from Norway, Sweden, Denmark, Finland and Iceland attended the ceremony near the town of Longyearbyen, in Norway's remote Svalbard Islands, roughly 1,000 km (620 miles) from the North Pole.
Norway's Prime Minister Jens Stoltenberg told the Norwegian news agency NTB: "The vault is of international importance. It will be the only one of its kind; all the other gene banks are of a commercial nature."
Fenced in and guarded, with steel airlock doors, motion detectors and polar bears roaming outside - the concrete facility will, its backers say, be the most secure building of its type in the world.
This is polar bear country
Norway's Agriculture Minister Terje Riis-Johansen has called the vault a "Noah's Ark on Svalbard."
The vault's purpose is to ensure survival of crop diversity in the event of plant epidemics, nuclear war, natural disasters or climate change; and to offer the world a chance to restart growth of food crops that may have been wiped out.
At temperatures of minus 18C (minus 0.4F), the seeds could last hundreds, even thousands, of years. Even if all cooling systems failed, explained Mr Riis-Johansen, the temperature in the frozen mountain would never rise above freezing due to the permafrost on the mountainside.
The Global Crop Diversity Trust, founded in 2004, will help run the vault, which is planned to open and start accepting seeds from around the world in September 2007. The bank is eventually expected to house some three million seeds.
"This facility will provide a practical means to re-establish crops obliterated by major disasters," Cary Fowler, executive secretary of the Global Crop Diversity Trust, said in a statement.
Fowler, who led a feasibility study on the project, said crop diversity was also threatened by "accidents, mismanagement, and short-sighted budget cuts".
Already, some 1,400 seed banks around the world, most of them national, hold samples of a country's crops. But these banks "can be affected by shutdowns, natural disasters, war or simply a lack of money," said Mr Riis-Johansen.
While Norway will own the vault itself, countries sending seeds will own the material they deposit - much as with a bank safe-deposit box. The Global Crop Diversity Trust will help developing countries pay the cost of preparing and sending seeds.