The two wells, at Ratva, near Kohtla-Järve in Ida-Viru County, are man-made, and were put in place to regulate subterranean water levels from a nearby oil shale mine after it closed in 2013.

Once mines and quarries close, pumping work stops meaning that the facilities often get inundated with groundwater – the Rumu quarry is another example.

In the case of deep mines, this would be a problem for agriculture and forestry, if the surrounding area were to become too waterlogged, hence the installation of the wells, which in the case of Ratva are 40m deep (a fuller explanation clipped from an information sign on-site is below).

The flooding so far is only a trickle, and has arrived with the milder temperatures in recent days, but is likely to build up as spring arrives – last year, the water level rose to several meters at the peak of flooding.

The outflow then makes its way via a culvert to a natural stream which is a tributary of the Ojamaa river, itself a tributary of the Purtse, which flows into the Gulf of Finland.

Another, more well-known "witches' well" is at Tuhala, near Tallinn, a location also likely to attract plenty of visitors once the levee breaks, so to speak.

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