Queimadas, Brazil

This island is no tropical paradise. Snake Island, as it's known, is home to an estimated 2,000-4,000 golden lancehead pit vipers - one of the most venomous snakes in the world. With the entire 106-acre landmass closed off to the public, only select researchers vetted by the Brazilian government are allowed to step foot on this remote, barren rock in the Atlantic. And for good reason - the island's snake population is so dense, there's reportedly one snake per square meter in the rainforest areas.

The climate here is temperate, with temperatures ranging from 65°F in the winter to 81°F in the summer. But the persistent bureaucratic hurdles to access this island make it a poor choice for all but the most intrepid thrill-seekers. Queimadas is not for the faint of heart.