(CNN) — With the largest coral reef ecosystem in the world, the Great Barrier Reef is one of seven natural wonders of the world and a UNESCO World Heritage Site. It's also the world's top travel destination, according to U.S. News & World Report's 2016-17 best destination rankings, released Tuesday. "It's a once in a lifetime vacation, and it's been in the news recently because of coral bleaching," said Erin Shields, travel editor for U.S. News, in a statement. "Travelers need to see it soon because there might not be as much left."
When sea temperatures rise, tiny algae living in the corals, called zooxanthellae, are expelled, turning the coral white. The reef covers an area of 344,400 square kilometers and includes about 600 continental islands, 3,000 coral reefs and 150 inshore mangrove islands.
U.S. News analyzed more than 250 destinations using a methodology that combines expert analysis and traveler opinions.
Best places to visit 2016-17:
25. Budapest, Hungary
24. Argentine Patagonia, Argentina
23. San Francisco, California
22. Bali, Indonesia
21. British Virgin Islands
20. Grand Canyon National Park, U.S.
19. Washington, D.C.
18. Cairo, Egypt
17. Hong Kong
16. Amsterdam, Netherlands
15. Yellowstone National Park, U.S.
14. Rio de Janeiro, Brazil
13. Sydney, Australia
12. Barcelona, Spain
11. Cape Town, South Africa
10. Maui, Hawaii
9. New York
8. Rome, Italy
7. London, England
6. Cusco, Peru
5. Tokyo, Japan
4. Florence, Italy
3. Bora Bora, French Polynesia
2. Paris, France
1. Great Barrier Reef, Australia