This anonymous structure facinates me. Behind this little door in the mountain are there several large halls, and it contains all kind of plant seed from all over the world. Kind of a safety net in case some plants should disappear, and we need to replant them.  A way of securing the worlds food supply in the long run.  Since its contents it highly presious and fragile, it is not allowed to go inside the vault.
One of the resons for choosing Svalbard  and the Arctic for the location it is due to the cold frozen climate that allows for it to keep the seeds safe even if should loose its power supply.

You can read more about the Global Seed Vault here

-Ray