The imposing medieval castle with eight crenellated towers 28m (92ft) high, was built in the 10th century to protect the population from attacks by the Moors and the Normans. It was then extended to its present size in the 12th century by Afonso Henriques, the first king of Portugal, who was baptized in the small Romanesque chapel next to the castle.
To experience medieval Guimarăes, visit the city in the first week of August for a festival of medieval art and costume. The three-day celebration dates from the middle of the 15th century, and includes a torchlight procession and a medieval parade.

It is possible to visit the city on a daytrip from Porto or Braga, but it is worth staying at one of the two pousadas in town. The award-winning Pousada Santa Marinha da Costa is the best choice, a 12th century monastery set on a hill overlooking the city, with an elaborate rococo façade.

Guimarăes was declared a World Heritage Site because:
"Guimarăes is of considerable universal significance by virtue of the fact that specialized building techniques developed there in the Middle Ages were transmitted to Portuguese colonies in Africa and the New World, becoming their characteristic feature. The early history of Guimarăes is closely associated with the establishment of Portuguese national identity and the Portuguese language in the 12th century. An exceptionally well-preserved town, Guimarăes illustrates the evolution of particular building types from the medieval settlement to the present-day city, and particularly in the 15th-19th centuries."