Sanmenhai Geopark, with its blue waters and mysterious mountains, is a must-see.

Sanmenhai Scenic Area in Fengshan is the only water-filled sinkhole in the world recognized by the World Cave Association. It is a tourist attraction with international standards, integrating natural landscapes, longevity culture, and revolutionary historical sites. The Sanmenhai skylight group is the largest and most spectacular. There are seven karst skylights (sinkholes) here, and several square kilometers of Minghu and Anhu are connected by the outlet of the underground river in the slope heart. Three skylights can be entered by boat through natural channels, giving people a mysterious feeling of "mountains in the sea and doors on the sea". This is why it is named "Sanmenhai".