Shark Bay, Western Australia

At Australia's westernmost edge, life's deep past and teeming present share one bay. Shark Bay's hypersaline shallows grow stromatolites — layered mounds built by microbial communities of a kind that dominated the planet for billions of years — while the world's largest seagrass beds, some 4,800 square kilometres, sustain one of the most important dugong populations anywhere. Five endangered mammal species cling on across its islands and peninsulas. UNESCO inscribed Shark Bay in 1991.