[4][5][6][7] The hill was first used by Celtic tribes, then by Phoenicians, followed by Greeks and later the Carthaginians as a defensive outpost that was later expropriated successively by the Romans, the Suebi, the Visigoths, and the Moors.

[7] According to an oft-repeated legend, the knight Martim Moniz, noticing that one of the doors to the castle was open, prevented the Moors from closing it by throwing his own body into the breach, thus allowing Christian soldiers to enter at the cost of his own life.

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.

These public works continued from 1449 until 1452, with additional payments being made for labor and materials to convert the building from a fortified castle to a royal residence.

[12] Later that century, German humanist Hieronymus Münzer spent five days in Lisbon in 1494, and learned about the lions, claiming to be the most beautiful wild beasts he had ever seen.

[13] As the royal palace, the castle was the setting for the reception by King Manuel I of the navigator Vasco da Gama when he returned from discovering the maritime route to India 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.

On 6 November 1648, Nicolau de Langres was called upon to take over the design, execution and construction of a new fortification that would surround the Castle of Saint George and the city walls of Lisbon.

In 1673, the Soldiers' Hospital, dedicated to São João de Deus (St John of God), was installed on the grounds beside 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 initiated by master Custódio Vieira.

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 on site.

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.

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.

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 northern Portugal.