The place where the ponds are located is called Oshinohakkai, which literally translates to "eight springs of Oshino".
The waters of the spring are unbelievably clear. You can see all the way to the bottom. A varied collection of underwater plants and colorful fishes (the large kois are amazing) inhabit the ponds.
You can take a sip of the fresh spring water if you fancy it.
It amazing how the place is preserved. Knowing the Japanese, the springs will still be in their pristine state decades from now.