Around the world there are believed to be as many as 900 thousand islands that range from small rocky outcrops to wealthy, thriving communities. There’s such a huge variety that depends on how they were originally formed and their location… and, while many may be quite similar to one another, there are some that stand out as being truly unique. From one of the most biodiverse places on the planet, to manmade ones and those with vast natural resources, it’s time to take a tour of the 15 most rare islands on earth.