A well that, according to preserved engravings and several historical maps and plans, stood in the middle of the Fish Market was probably established at the end of the 14th century and probably served until 1820, when it was buried. It had stone timbering with decorations and one or two levelling steps. A forged lattice decorated it from the 17th century.

A marked well on several plans helped to quite accurately estimate where it was originally located. In the summer of 1999, exploration work began in the middle of the square. After excavation of the exploration shaft, a fragment of brick vault was found at a depth of two metres under the pavement, which was well arched after filling the well. The vault was supposed to prevent the soil from further sinking under the paving of the square, and it fulfilled this task perfectly. Below it was a well-preserved stone well with a diameter of 1.4 metres, completely covered with clay. The backfill gradually settled to the bottom level at a depth of 14.5 metres. After cleaning, the well was repaired and missing stones were added.

An interesting finding was made at 11 metres. At this level, the lining is a walled octagonal wreath of oak wood, which means that the well was further deepened by 3.5 metres, probably due to a drop in groundwater. This is confirmed by the surface of the stones, which above this wreath are marked by pulling chains much more than they are below it.

From the moment when the pumping of water was stopped after the completion of the repairs, the water column of the well rose to a height of 3 metres. Now the well is temporarily covered, waiting to be reintegrated into the square as it was in the past.