Tuhala River is a branch of the Pirita River that is 26 kilometers long, with 6 of those kilometers running underground as three separate branches. Water starts to spout up from the well and flood the area when excess water from the Mahtra swamp fills up the underground river and the overflowing river water seeks an escape through the well. The quantity of water flowing through the Tuhala River must be at least 5000 liters per second in order for the river to overflow. However, the water spouting out of the well comes at only 100 liters per second.
According to local legend, the Witches Well boils over when the witches of Tuhala make a sauna below the ground and beat each other with birch branches, causing a commotion on the surface.
Video by Estonian Public Broadcasting