Castillo de San Marcos, Medieval fortress in Sanlúcar de Guadiana, Spain.
Castillo de San Marcos rises on a hilltop above Sanlúcar de Guadiana with thick round towers and sturdy stone walls. From its elevated position, the castle commands a view of the Guadiana River and the Portuguese lands directly across the water.
Portuguese forces built the original fortress in the 13th century to control this border territory. Later, it came under the rule of the Kingdom of Castile as the kingdoms worked to define their frontier lands.
The fortress shapes the local identity and remains the most recognizable landmark of Sanlúcar de Guadiana for both residents and travelers. It stands as a focal point where people come to understand the shared border story and observe the lands across the water.
The climb to the castle follows a steep path from the village center, so visitors should wear proper shoes and allow time for the walk. The elevated position means exposure to the elements, so it helps to visit on clear days and bring water.
The fortress directly faces its Portuguese twin, Castelo de Alcoutim, across the Guadiana River, creating a physical reminder of medieval competition between two kingdoms. This neighbor relationship reveals how close the frontier was and how crucial this river valley proved for defense on both sides.
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