Located northwest of Lisbon, in the far west of the al-Ândalus, by the tenebrous sea, Sintra was described by several Muslim authors. In the 10th century it was already an important population centre, although not confined to the Moorish castle, either because of its small size and difficult access, or because it was far from agricultural areas.
Endowed with two castles of "extreme solidity", one of them strategically built on one of the peaks overlooking the mountains - the Moorish castle - Sintra was mentioned later by al-Himyari as one of the villages that depended on Lisbon in al-Ândalus, being located near the sea and permanently immersed in an intense haze that did not dissipate and that makes Sintra a unique place.
The Moorish Castle is thought to have been built in two distinct phases, the earliest of which dates back to the 9th / 10th centuries, similar to other Peninsular cases, and corresponds to the period of fortification of the Atlantic coast carried out by the Muslim authorities against Viking attacks. However, more recent work has pointed to chronologies of occupation of the site around the 10th and 11th centuries.
The Moorish Castle, which was part of the Islamic coastal defence system that operated from the Sintra coast and was part of the district of Lisbon, had the particularity of serving as a lookout point for access by sea and land and, from there, it was possible to establish communication with other defensive posts at medium and long distances. However, this would only be possible on days with good visibility, which is not always a reality in Sintra, which is quite subject to the fog that lingers there. The warning system that operated from the Moorish Castle and other points in the Sintra mountains was very limited and often became inactive. However, as an alternative and a complement, there were other lookout posts and visual signal relays along the coastline.
However, throughout its history, this castle has also served as a guide for those sailing on the Ocean Sea but it eventually lost its strategic importance and was abandoned. At the end of the 15th century, only a few Jews inhabited the castle in order to comply with the royal order in force at the time, which forced them to live isolated from the rest of the population. When the ethnic and religious minorities were definitively expelled from the country, the Castle was definitively abandoned.
As time went by, the Castle became more and more dilapidated. With the earthquake of 1755, what was left of the original structure was further ruined. Only in the 19th century, during the reign of King Fernando II, was the castle completely restored. Currently, little of its original structure can be found. Only the base of the towers and the walls are part of the original foundation. From the top of its walls it is possible to admire a unique landscape that makes Sintra the special place it is.