10. Australia
The Great Barrier Reef, the world's largest collection of coral reefs, is a natural phenomenon not to be missed. Australians are arguing fiercely over manmade threats to its existence (and no one is happy about that).Once you've had a chance to explore that magical underwater realm, head to the Australian state of Tasmania, an island 240 kilometers (149 miles) off the mainland coast. The Tasmanian Wilderness, a UNESCO World Heritage Site, includes one of the last surviving temperate rainforests in the world.
To see the wilderness up close, try hiking the stunning 65-kilometer (40-mile) Overland Track. It takes about six days for hikers (who must book the trip in advance), but day-trippers can take short hikes starting at Cradle Mountain Visitor Centre and Dove Lake.