This is because the microorganism named Hikarimo floats on the surface of the water from April to June and reflects the light coming from the hole that is open on the ceiling and lights the water.
This Hikarimo, it is possible to live if the water is beautiful. So the habitat is limited, and it is very rare for "the gold pond" to periodically emit light in the same place every year like it seems.
Since ancient times, people felt a very mysterious to this shine. And so there are some Benten-sama,Yebisu-sama,Torii and Jizo-sama around "this gold pond".This pond was a place of faith in various religions.
There is a golden pond in the crack of this rock.
A golden pond looking from the outside of the rock.
People who have lots of gold laugh with such expressions.
A shrimp shaped like a stone attached to the rock.
Was it an ancient tomb ? Hole above the rock with the well.