1.The Guatemala Sinkhole, Guatemala city, Guatemala

 

2.Great Blue Hole in Belize (Source: huanqiu.com)

3.The Cave of Swallows in Mexico

 

4. Zacaton in Mexico

5. Xiaozhai in Chongqing, China

 

6. Bimmah in Muscat, Oman

7. Sima de las Cotorrasin in Mexico

8. The pastor's blue hole in long island, Bahamas

 

9. Sima Humboldt Bolivia, Venezuela

10. Minye in New England island, Papua New Guinea (Source: huanqiu.com)