Castro Marim - Forte de São Sebastião

Fortification - Iron Age, Roman Period, Modern Age e Contemporary Period (18107)
This fort is located about 35 m high on the Cerro do Cabeço, south west of the Castro Marim castle hill, on the right bank of the Rio Guadiana . This elevated position overlooking the castle's hill allowed the reinforcement of its defence, as well as the protection of the estuaries located south of it. Archaeological works on this site identified materials and structures framed in five distinct occupation stages, the oldest being the First Iron Age (7th / 5th century BC) and the most recent in the 19th century. Identified traces from the First Iron Age are scarce, matching only rare structures and ceramic artefacts (amphorae and handcrafts). Structural vestiges from the Republican Roman period (late 2nd century / first half of 1st century BC) were found, as well as a set of diverse artefacts (common pottery, Campanian pottery, Italic amphorae). The São Sebastião fort was built during the Portuguese Restoration War in the year 1641 (reign of D. João IV), with the strategic purpose of reinforcing the defence of the castle of Castro Marim, making the protection of the entrance of the Guadiana river more robust. Making use of local raw materials in the first stage of construction (1641), the fort had a modest size, an irregular blueprint with four middle bastions and a drawbridge entrance facing north. In 1660, a wall was raised with five bastions, several curtain walls that linked the fort to the castle of Castro Marim, and two gates: São Sebastião (near the fort) and Santo António (on the castle hill). This irregular polygon shaped structure practically enclosed the modern era town and was reinforced by the Santo António's ravelin (semi-circular structure, outlined by stools meant for artillery pieces), located in the Cerro da Rocha do Zambujal, guaranteeing the control of the Guadiana estuary. These fortifications were highly damaged by the several earthquakes that occurred during the 18th century, with special emphasis on the great earthquake of 1755, which motivated the renovation that was carried out during the first decades of the 19th century.


The exterior of the Fort can be visited freely. Inside visits require booking.

Visit conditions

By booking



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    How to get there? Best practices

    Best practices

    Good practices when visiting archaeological sites

    To visit an archaeological site is to connect with our origins, to understand our path and evolution as a species integrated in the environment, and to respect and safeguard our heritage so that future generations can also visit and enjoy it.

    Walking the paths and enjoying the structures and archaeological pieces that survived over time, fosters the understanding of what is different, but also of what is common among different populations: basically, what identifies us as Homo Sapiens.

    More than just vestiges and ruins of the past, archaeological sites showcase our capacity for creative thought, adaptation, interconnection, comprehension and resilience. Without these traits we would not have been successful as cultural beings participating in an ongoing evolutionary process. These sites also allow to consider choices made in the past thus contributing for decisions in the present to be made with greater awareness and knowledge.

    Archaeological sites are unique and irreplaceable. These sites are fragile resources vulnerable to changes driven by human development. The information they keep, if destroyed, can never be recovered again.

    As such, the Directorate-General for Cultural Heritage (DGPC) invites all visitors to enjoy the beauty and authenticity of these sites, while helping to preserve them for future generations by adopting the following set of good practices:

    • Respect all signs; 
    • Do not try to access fenced areas; 
    • Do not climb, sit or walk on archaeological structures and remains; 
    • Respect areas where archaeological excavations are being carried out, not disturbing them; 
    • Do not collect materials or sediments;
    • Do not write or make graffiti on archaeological structures; 
    • Put the garbage in appropriate containers. If none exist, take the garbage with you until you find a suitable container; 
    • Leave the archaeological site as you found it; 
    • Do not drive bicycles or motor vehicles over archaeological sites; 
    • Respect and protect the plants and animals that live in the areas surrounding archaeological sites;
    • Report signs of vandalism or destruction to DGPC or Regional Directorates of Culture (DRC);
    • Share the visiting experience and the archaeological sites, as a way of raising awareness to their preservation and making them better known;
    • Do not buy archaeological materials and report to public security authorities, DGPC or DRC, if you suspect that archaeological materials may be for sale.

    Further information:

    AIA / ATTA (2013) – Guide to best practices for archaeological tourism. 

    Raposo, J. (2016) – Código de conduta para uma visita responsável a sítios arqueológicos. In Sítios arqueológicos portugueses revisitados: 500 arqueossítios ou conjuntos em condições de fruição pública responsável. Al-madan, 2ª série, p. 20 – 77. 

    DGPC contacts

    Phone: +351213614200 | Email:


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