In this shallow stretch of Shark Bay in Western Australia, a natural record of Earth"s history lies just below the water"s surface. Hamelin Pool Marine Nature Reserve protects our planet"s biggest collections of stromatolites—small sedimentary rock towers built up over the centuries. Each layer captures fossils of the many microorganisms that populate our oceans. Some of the stromatolites in Hamelin Pool contain fossil specimens that are 3 billion years old. When you"re strolling down the boardwalk of Hamelin Pool, you"re walking over an unparalleled collection of biological history. The view of the Indian Ocean"s not bad either.