Castle of Almourol built
1171 CE.
Shown on the map at 39.462°, -8.384°.
The Castle of Almourol is a medieval castle atop the islet of Almourol in the middle of the Tagus River, located in the civil parish of Praia do Ribatejo, 4 kilometres (2.5 mi) from the municipal seat of Vila Nova da Barquinha, in Portugal's Oeste e Vale do Tejo region. The castle was part of the defensive line controlled by the Knights Templar, and a stronghold used during the Portuguese Reconquista.
Text from the Wikipedia article Castle of Almourol, licensed CC BY-SA 4.0.