Known as "Witches' wells" (Estonian: Nõiakaev), these particular springs are usually the result of human activity left over from abandoned oil shale mines (see gallery).

In the case of Ratva, the two, 40-meter deep boreholes were completed just five years ago, and redirect floodwater accumulated in a nearby disused mine into a drainage channel.

Without some sort of drainage system once mines and their associated pumps were no longer functioning, excess water could potentially have caused damage to nearby agricultural and forested land.

Most of the witches' wells spring forth with the end-of-winter thaw, as at Ratva, while natural springs often inundate the surrounding area too.

Any time from late February through to April is often known as the "fifth season," no longer winter but not quite yet spring, and is as such accompanied by melt-water activity like this.

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