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.”

The Great Barrier Reef is facing rising sea temperatures that have led to mass coral bleaching, Australian scientists say.

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.

Grand Canyon National Park was named the top U.S. destination, while the British Virgin Islands took the top Caribbean spot and Vancouver earned the top Canadian spot.

Rome was the top spot in Europe while Cape Town, South Africa, topped the Africa/Middle East list. Bali was the top Asia spot.

For Central and South America, Galapagos Islands came out on top while Oaxaca was named the No. 1 spot in Mexico.

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

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