The hilltop of Silves is one of those places that has been settled since prehistory, right by the Arade river which was navigatable until the late-middle ages, despite the city itself being somewhat far from the coast. The earliest fortification of the site seems to have been a Lusitanian castro before the Romans took over.
As the Umayyads invaded the Iberian Peninsula, the city was taken from the Visigoths in 756. Xelb as it was called, quickly became one of the most important cities in Muslim Iberia because of it's excellent geographical location. As the Caliphate of Cordoba fell, the city was conquered by Al-Mutamid the poet-king in 1052, who turned it into an important taifa or city-state. The Almoravids would take over the taifa states in 1091 and then give way to the Almohads in 1146 who would rebuild the castle as we see it.
In July 1189, King Sancho I of Portugal along with the Templars, Hospitallers, Calatrava Monks and a squadron of galleys sieged the city, which at this point was considered wealthier than Lisbon. A passing-by army of northern English and German Crusaders had joined the struggle, providing valuable assistance assaulting the walls and building siege engines, like trebuchets, assault towers, and a fearsome "porcupine" (a ram) that would demolish one of the citadel's towers. The Crusaders had taken the suburbs (the Medina) and set fire to it, but were unable to take the citadel. The Moors put up stiff resistance, which much exasperated the Crusader army. After severals months though, the situation within the castle walls became critical. According to a deserter, people chewed clay because water ran scarce and mothers killed their children to end their suffering. The city surrendered in September, and the Northern Crusaders would (yet again) be responsible for pillaging the city, against orders from the King.
Just three years later though, the Almohads under the command of Ya'qub Al-Mansur mounted a counter-attack that drove the Portuguese back to the Tagus river, defeating also the Castillians along the way. From 1228 until 1239, the southern region of Portugal, the Algarve was conquered by the Kinghts of the Order of Santiago. Silves would fall last in 1253, ending the Portuguese Reconquista.
Aerial view of the city. The buildings in the alcáçova, or citadel are long gone. It's been turned into a park and archeological centre.
The old entrance to the city, the Almedina Gate. According to Al-Mutamid, close by stood once the opulent Palace of the Balconies. It's a museum today.
The Alcáçova Gate, with a surely accurate life-size statue of King Sancho I.
