The Castle of Silves is a castle in the civil parish of Silves in the municipality of Silves in the Portuguese Algarve. It's believed that the first fortifications were built upon a possible Lusitanian castro, by the Romans or Visigoths. Between the 8th and 13th centuries, the castle was occupied by the moors who expanded it, making it one of the best preserved Moorish fortifications in Portugal, resulting in its classification as a National Monument in 1910.
The castle consists of an irregular polygon implanted on a hilltop overlooking the community of Silves, comprising four towers and seven crenellated posts, linked by walls with ardaves.
Two gates, the principal one between two towers and the Traitor's Gate carved into the northern wall. Alongside the principal gate is the guardhouse, constructed with a vaulted ceiling, and covered in tiles.
Within its courtyard are various subterranean structures, with accesses at soil level. The Cistern of Moura, is a 10 metres (33 ft) high, 820 square metres (8,800 sq ft) superficial area, with five naves marked by four orders of columns, interlinked by semi-circular archways. The Cisterna dos Cães, within the courtyard, is a vertical hole of 60 metres (200 ft) depth, that also supported water supply in the castle.