Just in case we destroy civilization
It's called the Svalbard International Seed Vault, and it is, officially, Plan B. There are plenty of other seed banks in the world, of course -- more than a thousand, designed as a source for planting in case seed reserves elsewhere are destroyed. But Svalbard will be there in case something happens to the rest of 'em; something like massive floods, nuclear war, asteroid impact or some other unforeseen doomsday.
The vault will be built deep inside a mountain on a remote island near the North Pole, more than 600 miles North of Norway, the country that's financing its construction. And they really thought of everything: it's high above sea level, in case the ice caps melt. If its source of power is cut, the permafrost surrounding it will act as a freezer, providing natural refrigeration. The need for human maintenance will be kept at a minimum; there will be no full-time staff, just one visit per year from someone to check up on the facility. "If you design a facility to be used in worst-case scenarios," the project's lead scientist said, "you cannot actually have too much dependence on human beings." Construction begins in March. Let's really cross our fingers that they'll never have to make a withdrawal at this bank.