. Great Barrier Reef Marine Park

You can't leave Australia without seeing the Great Barrier Reef. This World Heritage-listed natural wonder is one of the largest living structures on the planet. It's so vast, you can see it from outer space. For divers, snorkelers, island aficionados, and nature lovers, it's a bucket list destination.

In 1975, the Great Barrier Reef Marine Park was established to protect its fragile ecosystems. These include more than 3,000 coral reefs; 600 continental islands, including the beautiful Whitsunday group; 300 coral cays; and inshore mangrove islands.

One of the seven wonders of the natural world, the park stretches for 2,300 kilometers along the state of Queensland, on Australia's east coast (that's about the distance between Mexico and Vancouver).

Not surprisingly, the Great Barrier Reef is one of the best places to visit in Australia for diving and snorkeling. The astounding array of marine life includes soft and hard corals, more than 1,600 species of tropical fish, sharks, dugongs, dolphins, turtles, rays, and giant clams. Prefer to stay dry? You can see the reef from underwater viewing stations and glass bottom boats.

Travelers have many options for visiting the Great Barrier Reef. You can cruise around the islands, hop aboard a sightseeing flight, take day trips to the islands, or snorkel and dive the reefs. On the mainland, the main launching points for tours are Cairns, Port Douglas, and Airlie Beach.