Longdong was a sea cave, formed of the rock holed by the sea water. Later, people deepened it to 3.3 meters. There are 24 inscriptions of the period of Song, Yuan, Ming, and Qing not only in the cave but also on the cliff around the cave, including seal script, official script, cursive script, and running script. The biggest character is about 3 chis(equal to 1 meter), the smallest one is about 1 cun(equal to 1/30 meter). The inscription on the east of the cave written by Lin Tingyu and the one on the west written by Wang Tong are especially famous.