The Castle of Guimarães (Portuguese: Castelo de Guimarães), is the principal medieval castle in the municipality Guimarães, in the northern region of Portugal. It was ordered constructed by D. Mumadona Dias in the 10th century in order to defend its monastery from attacks by Moors and Norman.The castle is a military fortification grounded primarily in the late Romanesque period, and elaborated during the early Gothic epoch of Portuguese architecture.