In addition to the more outlandish theories, one user suggested it could be an aircraft door, while another said it may be a ...

Less sceptical commentators suggested that it could, indeed, be the entrance to an underground bunker or a seed vault ...

The Svalbard Global Seed Vault saw its largest number of new contributors in one day and now holds over 1.2 million seed varieties from 77 countries. Since 2008, the vault has been stockpiling ...