[1][2] The region became an important trading center frequented by Phoenicians and Carthaginians, thanks to the abundance of river and land routes connecting it to the southern portion of the peninsula.

It was destroyed and sacked by barbarian hordes, then Muslim Umayyad, who reconstructed the centre for their own necessities, where the name Myrtilis was shortened to Martula.

[2] Until the 18th century, the castle of Mértola continued to function as part of the first defensive line along the frontier with Spain, but began to diminish its military-strategic importance over time, before it was ultimately abandoned.

Between the 19th and 20th century, Mértola's economy was dependent on the exploitation of the mines of Santo Domingo, a major center for cupric pyrite extraction.

On 18 August 1943, by decree 32/973 (Diário do Governo, Série 1, 175), the heritage site was classified as a Imóvel de Interesse Público (Property of Public Interest).

[2] On 1 June 1992, the property fell into the administration of the Instituto Português do Património Arquitetónico (Portuguese Institute for Architectural Patrimony), under decree-law 106F/92 (Diário da República, Série 1A, 126).

[2] A revitalization project began in the 20th century saw the site transformed into a village museum with different areas specializing in different areas related to the castle's history: the keep tower was transformed into an observation deck as well as an interpretative centre presenting Roman, Visigothic Nucleus, Christian and Islamic collections that include one of the best collections Portuguese Islamic art (such as pottery, coins, and jewelry).

The Castle of Mértola is situated in an urban area on the hilltop, implanted in the rocky landscape bisected by the Guadiana River and the Ribeira de Oeiras.

Alongside the keep tower is a sculpted white marble, relief coat-of-arms of António Rodrigues Bravo, High-Courier (postal official) of the town.

[2] The Carouche Tower, in the southwest, is a cubic 4.7 metres (15 ft) wide, with access from the battlements and covered by terrace, broken by door and window.