Today we are in one of the most important historical centers of Bergamo: let's go and discover Borgo di Terzo. Characterized by a very particular urban structure that is given by the presence of a curtain of buildings along which a seriola derived from the Cherio river flows. Which had a very important role from the mid-thirteenth century to create a series of buildings for the processing of iron and for the grinding of cereals. The reason for these activities can be attributed to the presence of the river that provided enough hydraulic energy to run these machines. Entering the village we admire an important medieval building, the Torrazzo, the seat of the duty where iron was deposited to pay taxes on production and which today still preserves these important medieval features; it was, among other things, the only building beyond the seriola. An important reference was the Terzi family, a small local seignory owner of all the mills in the village. We then admire another series, built in the sixteenth century, an extremely important model to highlight how the water resource of this wonderful town was used.