When you visit at Jeju island, I strongly recommend lava forest named 'Gotjawal'.
And I introduce Dongbaek-Dongsan which is one of 4 Gotjawals in Jeju island.
Actually Jeju island is a volcanic island which erupted a million years ago. After that lava covered the whole island and a forest has been growing.
There are full of lava rocks under the ground of the lava forest. So trees can't have their root properly. We call the root 'Buttress root'. They have to grab the rocks firmly to survive.
Quite interesting thing in 'DongBaek-Dongsan' is that it has so many wetlands. They say there are 68 water pits in the forest. It is affected by the type of Pahoiehoie lava flow.
Dongbaek-Dongsan is the only place where 'Jejugosarisam' exists in the world. It is registered as second degree endanger plants.
In the middle of the forest you will meet a small lake. It is called 'moemulggak'. You can find diverse plants and reptiles as well as migrant birds.
You can't miss mushrooms in the forest. Because a forest is a home of mushrooms. Even though there are so many mushrooms it doesn't mean they are all edible. You should be careful of that.
Tumulus is a pile of lava ricks by pahoiehoie lava flow. Time after the pile of rocks collapsed like the picture. Rain water can't penetrate into the ground properly so it becomes wetland. We call this wetland 'dry wetland'. Some times sun light gives magnificent view in the wetland.
Look at the tree. The two roots connected each other.
They look like twin trees or a mother and a child. Two trees grow from one root. Actually it's because this forest is a secondary forest which means people used to cut all trees in this forest for their living before a law of preservation made.
