They are hydraulic works. Usually, they are found on the landscapes of large rivers' banks.
The vertical millstone mills or water mills were used for cereal milling among other things.
They are mentioned in the Xth century. "Water mill" refers to a simple machine that took shelter under the bridge's arches or a simple shed. Some centuries later, there are spectacular constructions such as stone buildings that are provided with cutwaters. A bridge is an example that illustrates it. It groups several wheels joined by small bridges built using pieces of timber or a single board, they are called "bridges of planks".
Visitants can still observe those interesting medieval hydraulic constructions in a better or worse condition in Tordesillas.
There are six of them and are called:
1. De la Peña
2. So la Puente
5. Oslúa o Aslúa