Sanmenhai

Sanmenhai, also known as the Three Gates Sea, is a sinkhole system located in Bama Yao Autonomous County, Hechi, Guangxi Zhuang Autonomous Region, China. It is a significant karst landscape feature, characterized by a series of interconnected sinkholes and underground rivers.

The term "Sanmenhai" refers to the three main entrances or "gates" leading into the underground water system. These openings provide access to a vast network of submerged caves and waterways, making it a popular, albeit somewhat challenging, destination for cave diving and exploration.

Sanmenhai is considered a geologically important site due to its unique karst formations and the complex hydrological processes that have shaped the landscape. The water within the system is typically very clear, offering excellent visibility for divers. The area is also known for its biodiversity, though the subterranean ecosystem is not fully understood.

The sinkhole system contributes to the local water resources and plays a role in the region's ecology. It is also a growing tourist destination, attracting visitors interested in its natural beauty and unique geological features. Conservation efforts are in place to protect the fragile ecosystem of Sanmenhai from the impacts of tourism and other human activities.