In the 10th century, after the death of the Cont Hermenegildo (or Mendo) Gonçalves, his widow Countess Mumadona Dias takes over the County of Portucale and adopts two relevant measures: she founds, in downtown Guimarães, the Santa Maria Monastery (around 950) and, uptown, a castle known as of S. Mamede (between 950 and 957).
The construction of said castle was necessary to defend the new Monastery and the people that, in the meantime, settled near these two new structures. The construction of the Castle also served as a mean to assert her power towards other feudal lords. In December 4, 968 a decree grants the S. Mamede Castle to the Guimarães Monastery. This document has the first known reference of the fortification.
In the 10th century, the Countess Mumadona Dias founds, in Guimarães, two buildings of great significance for they still define the city nowadays: the Santa Maria Monastery and the S. Mamede Castle, so designated in her Testament.
As the historian Mário Jorge Barroca refers, the castle at the time would be much different than the one we know today, for these buildings were rudimentary, turrets were rare and there are no known watchtowers of the period.
The Castle was continuously altered so its original design mustn’t have much similarities to the current one. It is known that the Count Henrique did some renovations and, according to Mário Barroca, there are some remains believed to be from the 11th century. Later on, in the 13th and 14th centuries, King Dinis had the watchtower built along with eight turrets that flank the castle walls. There were some other interventions afterwards, during the reign of João I, which defined its last trace.
It is curious to notice that the Guimarães Castle was the first, in Portugal, to be photographed. These records allows one to see how the building was in the 19th century. The photos were taken by Frederick William Flower, an English trader that lived in Porto which was a photographic pioneer.
After centuries of abandonment and decay, the Castle was repaired in the 1930’s, under the extinct DGEMN (Directorate General for National Buildings and Monuments). The goal was to restore the most emblematic Portuguese site relating to the creation of the country.
The Guimarães Castle is a National Monument since 1910.