Castle of Alter do Chão: A Historic Fortress in Portugal

Visitor Information

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Country: Portugal

Civilization: Medieval European

Remains: Military

History

The Castle of Alter do Chão, located in the municipality of Alter do Chão in Portugal, stands on a site with a deep history stretching back to pre-Roman times. Initially, this location hosted an early settlement known as Abeltério, which played a role during Rome’s conquest of the Iberian Peninsula. Its strategic position lay along one of three Roman roads connecting Olissipo (now Lisbon) to Augusta Emerita (modern-day Mérida). During Emperor Hadrian’s rule in the early 2nd century CE, the original settlement suffered destruction by Roman legions, an event that likely led to the erection of a Roman fortification at the site to secure the area.

In later centuries, the settlement experienced further upheaval when the Vandals conquered the region, damaging the existing defenses. These fortifications were subsequently repaired during the Muslim occupation of the Iberian Peninsula, probably under the reign of Abd al-Rahman III in the 10th century. Archaeological evidence of this period includes five rows of carefully cut stones that reflect the architectural style common in the caliphal era, indicating significant reconstruction efforts.

The Christian Reconquest brought the castle under Portuguese control in the early 13th century. In 1216, King Afonso II ordered the repopulation of the area, signaling a renewed focus on its settlement and defense. The castle itself appears for the first time in written history in 1232 through a charter granted by the Bishop of Guarda, Mestre Vicente Hispano, during King Sancho II’s reign. Shortly afterwards, in 1249, King Afonso III issued a charter that mandated the castle’s reconstruction, underscoring its growing importance.

Throughout the late 13th century, King Denis I was closely associated with the site, visiting it multiple times and granting a new charter in 1292. This document notably affirmed that the town would remain under the direct authority of the sovereign, without an intermediate lord. The current structure of the castle dates largely from the reign of King Peter I, who ordered a comprehensive rebuilding effort on 22 September 1357, a date commemorated on a marble plaque above the main gate.

Subsequent monarchs, including Ferdinand I, John I, and John II, upheld royal ownership of the castle and carried out additional work to maintain and enhance the fortress. In 1432, notable campaigns addressed its upkeep, and by the late 15th century, it also served as a prison under the Duke Ferdinand II of Braganza. The castle’s military role continued into the 17th century during the Restoration War, when a barbette—an artillery platform—was added to the northeast wall, along with the rebuilding of defensive crenellations. In 1662, Spanish forces under Juan de Austria occupied the fortress.

Ownership of the castle shifted multiple times during the 19th and 20th centuries. In 1910, it gained recognition as a National Monument. The mid-20th century saw significant restoration and preservation efforts led by Portugal’s Directorate-General for National Buildings and Monuments, supported financially by the House of Braganza Foundation, which remains the current owner.

Remains

The Castle of Alter do Chão features a quadrangular layout characteristic of early Gothic military architecture. Constructed mainly from schist and granite, the fortress is located on a hill 270 meters above sea level, providing a commanding view of the surroundings. Its defensive walls are punctuated by six towers of various shapes and purposes, including two rectangular towers, two cylindrical towers positioned at the corners for enhanced defense, a smaller quadrangular turret midway along the northeast wall, and a square turret rising above the main gate on the southwest side.

Among these towers, the eastern corner tower stands out with its conical roof, a design element that adds both aesthetic distinction and weather protection. Along the walls runs a walkway known as a chemin de ronde, which allowed defenders to move quickly and safely around the perimeter; this path is shielded by crenellations—battlement openings for defense—supported by stone corbels, particularly evident along the eastern section. Some towers have been restored with square merlons and embrasures (the gaps used by archers or gunners) which date from renovations carried out in the 1940s.

The main entrance is marked by a pointed, or ogival, arch typical of Gothic design. Above it rests a coat of arms and the inscription recording the castle’s reconstruction date of 22 September 1357, commissioned by King Peter I. Passing through this gate leads into a parade ground, originally intended as an open space for assembling troops and conducting military drills. Within this area are a well and a cistern, both essential for providing water during sieges and everyday use.

Set back from the parade ground is the castle’s keep, or donjon, a sturdy square tower that rises 44 meters high. This central stronghold features a parapet topped by truncated pyramidal crenellations, a form of decorative and functional battlement design. Inside, the keep’s interior is divided into two floors, each vaulted with barrel ceilings reinforced by pointed stone arches. Light enters through mullioned windows—windows divided by slender vertical supports—illuminating these robust chambers. All doors in this tower maintain the Gothic pointed arch shape popular in the medieval period.

Adjacent to the keep lies the façade of what was once the mayor’s office, along with several other residential and administrative spaces. This area contains multiple entrances, windows, and a staircase, indicating that the castle was more than a military fortress; it also housed governing officials. Above the door to the mayor’s office, an inscription dated 1372 celebrates Fernão Rodrigues, steward to Dom Fernando Neto, Count of Arraiolos, as the person responsible for commissioning these works.

The castle’s surroundings include a narrow, landscaped strip of land that frames the fortress, complementing its presence within the landscape. The structure’s overall good condition today results from comprehensive restoration campaigns undertaken in the 20th century, which sought to conserve and consolidate the medieval fabric while respecting the site’s rich historical layers.