Lagoon Tongjong is located in Kunsan-ri, Thongchon County, Kangwon Province.

It was a bay created by the crustal movement about a million years ago. Later, its mouth was blocked by sediments brought by wind and waves for ages.

There grow oak, larch, Erman’s birch, acacia and pine trees and sweet briers around the lagoon.

Such sea fishes as flatfish, saury, herring, dace, gizzard shad, and such freshwater fishes as snakeheaded fish, carp and rainbow trout live in the lagoon. There are also shellfishes like corbicula, scallop, Nuttallia olivacea and oyster and freshwater king crab on the bottom of the lagoon.

Mud extracted from the bed of the lagoon is used for medical treatment. 

The lagoon is a holiday and tourist resort, as its sandy beach with red sweet briers in full bloom, clear and calm water, and an islet in the lagoon go well with the surrounding thick forests, unfolding a beautiful scenery.