5. Snake Island, Brazil
As the name implies, this 43-hectare island harbours one of the deadliest species of snakes in the world. Brazilians seem to think that you’ll find a snack on the island every 5 square meters, but the more plausible snake population is around 4,000. Chances are you’ll never find out for yourself unless you’re a biologist. The Brazilian government only allows a limited number of biologists and researchers to visit the island once a few years to study the snakes.