Castle of Almourol The Castle of Almourol is a medieval castle , located on a small islet in the middle of the Tagus River , in the civil parish of Praia do Ribatejo , from the municipal seat of Vila Nova da Barquinha , in the Portuguese Centre Region . The castle was part of the defensive line controlled by the Knights Templar , and a stronghold used during the Portuguese Reconquista . History . It is believed that the castle was constructed on the site of a primitive Lusitania n castro that was later conquered by the Romans during the 1st century B . C . E . It was later remodelled by successive invading forces , including the Alans , Visigoths and Moors , although it is unclear when the actual castle was established . In excavations carried out in the interior and exterior enclosures , various vestiges of Roman occupation were discovered , that included coins , millennium markers and Roman foundations , while medieval remnants such as medallions and two marble columns were also discovered in the castle ' s vicinity . The castle of Almourol is one of the more emblematic and cenographic medieval military monuments of the Reconquista , and best representation of the influence of the Knights Templar in Portugal . When it was conquered in 1129 , by forces loyal to the Portuguese nobility , it was then known as " Almorolan " , and placed in the trust of Gualdim Pais , the master of the Knights Templar in Portugal , who rebuilt the structure . The structure was reconstructed , starting in 1171 ( from an inscription over the principal gate ) and restored during the subsequent reigns . Losing its strategic place , it was abandoned resulting in its fall into ruins . In the 19th century , it was " reinvented " by idealistic romantics , which eventually led to interventions in the 1940s and 1950s , and its adaption as " Official Residence " of the Portuguese Republic . During this period , restorations had proceeded , transforming the physical appearance of the structure , including the addition of crenellations and bartizan s . The " DGMEN - Direcção - Geral dos Edifícios e Monumentos Nacionais " ( " Directorate - General of Buildings and National Monuments " ) , the forerunner of the IGESPAR first intervened on the site in 1939 , through the construction of the chemin de ronde in masonry , including reinforced concrete ; desmantlement and reconstruction of the corner of the keep ; repair and consolidation of the battlements , including the demolition of the tower ' s allure , reconstruction of a brick vault under the existing ; and reconstruction of the pavement in small stone . Around 1940 - 1950 , the spaces were adapted for its use as an official residence of the Portuguese Republic . At the end of this short term , the building ' s furniture was acquired by the Commission for Furniture Acquisition ( ) in 1955 , while an electrical grid was installed . Between 1958 and 1959 , there was some consolidation of the keep with concrete straps , a project to diminish the permeability of the courtyard and reconstruction of the interior walls of the tower by the " Escola Prática de Engenharia " ( " Practical School of Engineering " ) , as well as the reconstruction of a door that included doorposts and lintel s . In subsequent years , other projects occurred : in 1959 , the repair of the facade of one section of wall ; in 1960 , with the conclusion of the repairs to the exterior walls , the pavement and road access was improved by the " Direcção da Arma de Engenharia de Tancos " ( " Tancos Directorate for Weapons Engineering " ) . But , this roadway was improved with the reconstruction of a road that skirted the islet from the quay to the southern end of the castle , by the " Serviços de Engenharia do Estado Maior do Exército " ( " Service of the Army Corp of Engineers " ) . By 1996 , the walls were repaired , sections of the keep were preserved and the pavement in the castle restored . Owing to water infiltration , the castle began to show some signs of degradation by 2004 , including a few of the exterior walls . Architecture . The castle rises over a granite outcropping , it is approximately long and wide , in the middle of the Tagus River waterway , a few metres below its confluence with the Zêzere River in front of the town of Tancos . Although access to the Portuguese National Monument and fluvial islet is free , visitors to the structure must pay an inexpensive boat - ride across the river ( which is the only way for visitors to reach the castle ) . It is an irregular rectangular plan consisting of two enclosures : the exterior , lower level faces upstream with a traitors ' gate , and walls reinforced by nine tall circular towers ; and the interior enclosure , located in a higher elevation , whose walls are accessible by main gate to the main keep . The keep is three - stories tall and includes the original pads that supported the main truss . The remaining sentry towers are irregular , owing to the irregultar terrain . The keep is actually an innovation at this castle , appearing in the 12th century after the Castle of Tomar , the principal defensive redoubt of the Templars in Portugal . Similarly , the watchtowers were innovations brought into western part of the Iberian peninsula by the Order , and applied in Almourol . The interior is bisected by several masonry doorways that link the different parts of the castle . Two inscription stones mark the castle ' s history and its re - edification by Gualdim Pais ( over the main gate ) , as well as its Christian history ( from the cross carved into the space above an open window in the keep ) .