This is the third iteration of a cache at this feature that I am aware of. The previous two (GC5MTF6 & GC60M0N) have been archived for some time. There is no need to enter the structure to find the cache, it is outside close by.
Another relic from when this side of the island saw more activity than it does today? You can approach this location from a number of directions but you can not access it at night as Rabbit Island is strictly off limits after dark.
The cache is a micro container inside a small container (both "recycled") with log only so bring your own writing device. Please replace securely as found.
Happy caching.