Castelo de Montalvão

Portugal, Portugal

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Castelo de Montalvão in Montalvão, Nisa municipality, Portugal, was constructed in the 12th-13th centuries by the Knights Templar as a medieval border fortress along the Tagus Line to defend Portugal's eastern frontier against Castile, strategically positioned near the Tagus and Sever rivers.

Rebuilt during King Dinis's reign (1279-1325) under the Order of Christ, it featured an oval plan with schist walls, two quadrangular towers, a sloped alambor base, cistern, and two gates, though possibly never fully completed as noted in 1509 sketches by Duarte de Armas and the 1506 Tombo da Visitação.

Minor 17th-century reforms during the Restoration War integrated it into Elvas-linked defenses; now in ruins with a modern water tower inside, it evokes Alentejo's Templar heritage amid visual networks of atalaias.