Gruinard Island, Scotland
This tiny, oval-shaped Scottish island is just about 1.2 miles long by half a mile wide, but it’s one of the most dangerous places on the planet. No one has settled on this British “Anthrax Island.” It used to be the testing ground for biological warfare during World War Two. It was so contaminated that it was deemed out-of-bounds for half a century. Anthrax spores remain in the soil.