Castle of Seda

The Castle of Seda is a medieval fortification situated in the civil parish of Seda, within the municipality of Alter do Chão in the Portalegre district of Portugal's Alto Alentejo region. Constructed primarily from schist, limestone, and mortar, the site occupies a strategic position overlooking the Ribeira de Seda river. Its origins predate the current structure, as the location previously hosted a Romanized castro and an earlier fortification known as Arminho during the transitional period between Roman and Muslim occupations. The visible medieval settlement was established on these ancient foundations, leveraging the defensive advantages of the terrain which had been inhabited since at least the second century.

Historically, the castle played a pivotal role in the Reconquista after King Afonso Henriques conquered the settlement from the Moors in 1160. Following this victory, construction of the defensive walls likely commenced to secure the volatile frontier. The site was initially donated to the Knights Templar before being transferred to the Knights of Avis in 1271. Under the leadership of Friar Simão Soeiro, Master of the Order of Avis, the town received its first foral or charter in May 1271, a status later validated by King John I in 1427 and reissued by King Manuel I in 1510. By 1527, Seda served as the municipal seat with a recorded population of 184 residents under the jurisdiction of the Order.

Today, the Castle of Seda is owned by the Portuguese Republic and remains open to the public. Although the municipality was extinguished during administrative reforms in 1836, the site persists as a significant historical landmark representing the region's military and cultural evolution. While specific details regarding its current structural condition are sparse in available records, the remnants stand as a testament to the successive influences of Roman, Moorish, and Christian powers. The location continues to offer visitors insight into the medieval defensive strategies of the Alentejo borderlands and the enduring legacy of the military orders that shaped local development.