The Castelo de São Jorge is a medieval castle that overlooks Alfama, the oldest neighborhood in Lisbon. For centuries, the castle was the main residence of Portugal's monarchs.The Castelo de São Jorge is strategically positioned on top of the highest hill in Lisbon. Even before the arrival of the Romans, there were fortifications at this site but the current structure was built in the mid-eleventh century, during the Moorish era.During the second crusade, the castle was the last stronghold in the defense against the Christian army, led by Portugal's first king, Afonso Henriques. He finally captured the castle in 1147 with the help of northern European crusaders after a seventeen-week-long siege. It was a landmark victory in the Reconquista, the recapture of land on the Iberian peninsula from the Moors.