20. Snake Island, Brazil
Ilha da Queimada Grande, also known as Snake Island, is a small island off the coast of Brazil. Snake Island is home to the endangered, venomous golden lancehead snake (Bothrops insularis) which has an incredibly strong venom known to cause more human mortalities than any other group of snakes in either North or South America. The snakes have become trapped on the island due to rising sea levels and increased rapidly in population here. There is estimated to now be between one and five snakes per 10 square feet. Consequently Snake Island is completely off limits to the public.