renovated several times
This building is located on one of the steep streets leading down to the Ribera del Duero dock. From it's appearance it may go unnoticed, but it's worth your time to stop by, because inside the you can find the Historical Municipal Archive, an exhibition and an archeology museum. It is listed as a National Monument and is one of the most important civic buildings in Porto.
The building was built with stones in the fourteenth century, although it was later renovated and expanded several times. They added a couple buildings: The old currency house and one for customs. What we see today are two crenellated towers around a central rectangular courtyard.