The seed vaults are at the end of a 120m long tunnel

The temperature inside the Svalbard Global Seed Vault will drop to -18C (0F) in order to preserve the seeds.

Built deep inside a mountain, it aims to safeguard the world's crops from future disasters, such as nuclear wars, asteroids or dangerous climate change.

The first seeds are scheduled to arrive at the Arctic site in mid-February.

The Norwegian government is paying the $9m (£4.5m) construction costs of the vault, which will have enough space to house 4.5 million seed samples.

The collection and maintenance of the seeds is being co-ordinated by the Global Crop Diversity Trust, which has responsibility of ensuring the "conservation of crop diversity in perpetuity".

"The seed vault is the perfect place for keeping seeds safe for centuries," said Cary Fowler, the Trust's executive director.

"At these temperatures, seeds for important crops like wheat, barley and peas can last for up to 1,000 years."

Future proof

The seed vault will be built 120m (390ft) inside a mountain on Spitsbergen, one of four islands that make up Svalbard.

The site, roughly 1,000km (600 miles) north of mainland Norway, was chosen as the location for the vault because it was very remote and it also offered the level of stability required for the long-term project.

The vast collection is intended to act as insurance against disasters so food production can be restarted anywhere on the planet following a regional or global catastrophe.

"It is very satisfying to see the vault evolve from a bold concept to an impressive facility that has everything we need to protect crop biodiversity," said Terje Riis-Johansen, the Norwegian Agriculture and Food Minister.

Engineers are using the surrounding rock and permafrost as a "cold store", an energy efficient approach that has become popular in Norway.

"We believe the design of the vault will ensure that the seeds will stay well preserved even if forces such as global warming raise temperatures outside the facility," explained project manager Magnus Tveiten.