Tesla's patent 1,113,716 describes a way to make a fountain
that utilizes the smallest amount of energy to create
to push water up to a flared basin, where it overflows the
rim creating a circular cascade.

This man made waterfall will likely produce negative ions.

It is interesting that Tesla experimented with something
that most people perceive to be just a garden ornament.

Certainly the effect is visually pleasing and the negative ions
are healthy and improve the mood.
Perhaps the negative ions from a man-made fountain
can be utilize for radiant energy collection.