The slanted limestone layers of the meteorite crater put pressure on groundwater. The water spurts out of the ground in an uninterrupted stream through pipes placed 10-15 metres deep under the surface. There are particularly many artesian wells in Tiigi and Aia street and people can also drink crystal clear water from the well on the corner of Aia and Pikk street. You will see many fountains in the yards when you walk down Aia street - they are all artesian. They look especially beautiful in winter when ice sculptures form on the fountains.