Castle of São Jorge The Castle of São Jorge ( ; ) is a Moorish castle occupying a commanding hilltop overlooking the historic centre of the Portuguese city of Lisbon and Tagus River . The strongly fortified citadel dates from medieval period of Portuguese history , and is one of the main tourist sites of Lisbon . History . Although the first fortification on this hilltop date to the 2nd century BC , archaeological excavations have identified a human presence in the Tagus valley as far back as the 6th century BC . The first fortification was , presumably , erected in 48 BC , when Lisbon was classified as a Roman municipality . The hill was used by indigenous Celtic tribes , then by Phoenicians , Greeks , and Carthaginians , as a defensible outpost , that was later expropriated by Roman , Suebic , Visigothic , and Moorish peoples . During the 10th century , the fortifications were rebuilt by Muslim forces , that included the walls or " Cerca Moura " ( " Moorish Encirclment " ) . Kingdom . In the context of the Christian " Reconquista " , the castle and the city of Lisbon was conquered from Moors by Afonso Henriques , assisted by northern European knights during the Second Crusade : the Siege of Lisbon , which took place in 1147 , was the only notable success of that failed crusade . According to an oft - repeated legend , the knight , Martim Moniz , noticed that one of the doors to the castle was open , and he prevented the Moors from closing the door again by throwing his own body into the breach : he sacrificed his life but , in doing so , allowed Christian soldiers to enter . The taking of the castle helped Christians forces maintain the defense of Lisbon until the end of the 12th century . When Lisbon became the center of the Kingdom , in 1255 , the castle acted as the " alcáçova " : a fortified residence for Afonso III , in his role as governor . It was extensively renovated around 1300 by King Denis I , transforming the Moorish alcáçova into the " Royal Palace of the Alcáçova " . Between 1373 and 1375 , King Ferdinand I constructed the " Cerca Nova " or " Cerca Fernandina " , the walled compound that enclosed the entirety of the castle . During this construction , masters João Fernandes and Vasco Brás were responsible for the activities onsite . This wall , which partially replaced the old Moorish walls , was designed to encircle previously - unprotected parts of the city . Completed in two years , it had 77 towers and a perimeter of . The castle and the city resisted the forces of Castile several times during the 14th century ( notably in 1373 and in 1383 – 4 ) . It was during this period ( the late 14th century ) , that the castle was dedicated to Saint George by King John I , who had married the English princess , Philippa of Lancaster . Saint George , the warrior - saint , was normally represented slaying a dragon , and very was popular in both countries . It was during from this point that many of the Kingdom ' s records began to be housed in the " Torre de Ulisses " ( " Tower of Ulyssess " ) , also known as the " Torre Albarrã " , until the reign of Manuel I . For that reason , the Portuguese National Archive is ( still ) referred to as the " Torre do Tombo " ( literally the " Tower of the Archive " ( where eminent Portuguese chronicle rs like Fernão Lopes and Damião de Góis , once worked ) . On 9 December 1448 , Gil Pires was named castle carpenter , to replace Afonso Esteves , being paid 400 réis for his work . Between 1448 and 1451 , the carpenter was paid several stipends for his work within the palace . Similarly , the mason João de Alverca was paid 17 $ 016 for stonework ; there were also purchased of iron , totally 3 $ 792 ; acquisition of calcium oxide totally 3 $ 740 ; the purchase of raw wood for over 14 $ 500 ; and the purchase of roofing , tile and sand equal to 4 $ 474 . These public works continued from 1449 until 1452 , with additional payments for labor , calcium oxide , carpentry , cork , stonework and other purchases , including doors and windows , to convert the site from meager castle to royal residence . As Royal Palace , the castle was the setting for the reception for the navigator and national hero , Vasco da Gama , who had returned from discovering a maritime route to India : King Manuel I received him at the castle in 1498 . The castle also served as a theater in 1502 , when pioneering playwright Gil Vicente , staged his " Monólogo do Vaqueiro " , to honor the birth of Manuel I ' s son and heir , the future João III . Around the early 16th century , following the construction of the Ribeira Palace along the Tagus river , the old castle began to lose importance . An earthquake occurring in 1531 , further damaged the Palace of Alcáçova , contributing further to the site ' s decay and neglect . In 1569 , King Sebastian ordered the rebuilding of the royal apartments in the castle , intending to use it as his official residence . As part of the rebuilding , in 1577 , Filippo Terzi demolished one of the tower , near the principal facade of the Church of Loreto . However , many of the projects was never completed , with the young King ' s " disappearance " during the Battle of Alcácer Quibir . The Portuguese dynastic crisis that followed , opened the way for sixty years of Spanish rule and the castle was converted into barracks and a prison . On 30 December 1642 , during public reconstruction , Teodósio de Frias the Younger , replaced work completed at the time by his father Luís de Frias , and grandfather Teodósio de Frias . This was a part of a greater plan by the Spanish forces to recommission the fortification . But , with the Restoration Wars , the project was transformed into a Portuguese project . On 6 November 1648 , there was a request sent for Nicolau de Langres to takeover the design , execution and construction of a new fortification that would surround the Castle of São Jorge , and city walls of Lisbon . In 1650 , though , the site was visited by military architect Mateus do Couto . With the naming of Manuel do Couto , as master of the project , the reconstruction took on a new formality : João Gillot projected new walls in 1652 ; between 1657 and 1733 , the building project followed the plans of Manuel do Couto . In 1673 , the soldiers hospital was installed on the grounds , dedicated to " São João de Deus " , along the " Rua do Recolhimento " . At the end of the 17th century , the " Recolhimento do Castelo " ( " castle shelter " ) was constructed along the southeast angle of the courtyard , and in 1733 , new projects were projected by master Custódio Vieira da Silva . The great 1755 Lisbon earthquake severely damaged the castle and contributed to its continuing decay : apart from the walls of the old castle , the soldier ' s hospital and shelter were left in ruins . Further , the need to maintain a supporting force within the capital necessitated the expansion of the site ' s role of garrison and presidio . From 1780 to 1807 , the charitable institution Casa Pia , dedicated to the education of poor children , was established in the citadel , while soldiers continued to be garrisoned onsite . Inspired by the events of the earthquake and tsunami , in 1788 , the first geodesic observatory in Portugal was constructed at the top of one of the towers of the castle ; later referred to as the " Torre do Observatório " . Republic . As part of the commemorative celebrations marking the foundation of nationhood and restoration of independence ( ) , the government of António de Oliveira Salazar initiated extensive renovations at the site . Most of the incongruous structures added to the castle compound in previous centuries were demolished , under the supervision of the DGEMN , and there was a partial restoration of the " Recolhimento " . In addition , on 25 October 1947 , a monument dedicated to Afonso Henriques , presented by the city of Porto , of a replica created by Soares dos Reis ( in 1887 ) was installed on the grounds . In 1998 , the semi - rectangular spaces , columns and cistern were adapted into the museum " Olissipónia " . On 22 August 2006 , Direcção Regional de Cultura Lisboa ( DRCLisboa ) defined a special protection zone , that included the Castle of São Jorge and the rest of the walls of Lisbon , the " Baixa Pombalina " and various properties that were already classified as cultural heritage . The " Conselho Nacional de Cultura " ( " National Council on Culture " ) proposed shelving this definition on 10 October 2011 , which was supported by IGESPAR Architecture . The castle is located in the centre of city of Lisbon , over an escarpment , while many of its walls extend around the citadel into the civil parishes that surround it to the east and south . The castle ' s footprint is roughly square , and it was originally encircled by a wall , to form a citadel . The castle complex consists of the castle itself ( the " castelejo " ) , some ancillary buildings ( including the ruins of the royal palace ) , gardens , and a large terraced square from which an impressive panorama of Lisbon is visible . The main entrance to the citadel is a 19th - century gate surmounted by the coat - of - arms of Portugal , the name of Queen Maria II , and the date , 1846 . This gate permits access to the main square ( " Praça d ' Armas " ) , which is decorated with old cannons and a bronze statue of Afonso Henriques , the Portuguese monarch who took the castle from the Moors . This statue is a copy of the 19th - century original by the romantic sculptor , António Soares dos Reis , which is located near Guimarães Castle in central Portugal . The remnants of the royal palace are located near the main square , but all that is left are some walls and a few rebuilt rooms like the " Casa Ogival " . It now hosts the " Olissipónia " , a multimedia show about the history of Lisbon . The medieval castle is located toward the northwest corner of the citadel , at its highest point . Hypothetically , during a siege , if attackers managed to enter the citadel , the castle was the last stronghold , the last place available to take refuge . It is rectangular in shape , and it has a total of ten towers . A wall with a tower and a connecting door , divides the castle courtyard into halves . A series of stairways allow visitors to reach the walkway atop the wall and the towers , from which magnificent views of Lisbon can be enjoyed . The " Tower of Ulysses " ( where the " Torre do Tombo " archive used to be ) now has a periscope that allow tourists to have a 360 - degree view of the city . Apart from its main walls , the castle is protected , on its southern and eastern sides , by a barbican ( " barbacã " ) , a low wall that prevented siege engines from approaching the main castle walls . The northern and western sides of the castle , on the other hand , were naturally protected by the steep hillside sloping downward from the castle ' s foundations . The castle is also partially encircled by a moat , now dry . The main entrance is fronted by a stone bridge across the moat . On the west side , there is a long curtain wall extending downhill , ending at a tower ( the " Torre de Couraça " ) . This tower served to control the valley below , and it could also be used to escape , in case the castle was taken by enemies .