Notice the collection of industrial-grade basalt grinders. The larger "hour-glass-shaped" ones (one is visible on the right) fit over a stationary cone (just left of center). The grain was inserted into the top and came out ground at the bottom.
Capernaum is in a basalt region of the country.
These grinders may have been used here, as wheat and barley can be grown in the region, but it may also be that the grinders themselves were "manufactured" here at Capernaum. Matt. 18:6 ". . . but whoever causes one of these little ones who believe in Me to stumble, it is better for him that a heavy millstone be hung around his neck, and that he be drowned in the depth of the sea."