Impenetrable
Put an island in the middle of the tropical bit of an ocean (here Reunion Island in the middle of Indian Ocean).
Make it receive tons of sunlight and tons of rain.
Fill it with a hot and moist atmosphere before you also fill it with mountains with sides just less vertical than walls.
There you go. You have it.
Impenetrable.
Also, it may look like a giant mess but it has to be another perfect natural organisation where, if you remove one element, the entire assemble may collapse.
Pretty much like me after trekking there for over a week.
Impenetrable
Put an island in the middle of the tropical bit of an ocean (here Reunion Island in the middle of Indian Ocean).
Make it receive tons of sunlight and tons of rain.
Fill it with a hot and moist atmosphere before you also fill it with mountains with sides just less vertical than walls.
There you go. You have it.
Impenetrable.
Also, it may look like a giant mess but it has to be another perfect natural organisation where, if you remove one element, the entire assemble may collapse.
Pretty much like me after trekking there for over a week.