In the year 1920 while working on the municipal park, construction workers discovered a flat, disc-shaped chopper at a depth of 1.7 metres. It is the oldest evidence of the grinding of solid rock in the Hamburg city area. The surface, however, is very weathered: After all, the find had been lying in the ground for more than 7 000 years. The function of such choppers has not been determined, yet; they hardly ever show traces of use.