Forte São João in Bertioga is Brazil's oldest surviving colonial fortress, originally constructed in 1532 as a wooden palisade by Portuguese explorer Martin Afonso de Souza to protect against indigenous attacks. Rebuilt in masonry in 1547 after destruction, it stands as a crucial monument of Portuguese maritime expansion and Brazil's foundational history. Located along the Atlantic coast, the fortress played an essential role in controlling the Bertioga channel and defending early settlements. Today, the fort welcomes visitors free of charge Tuesday through Sunday, offering guided tours that explore its architectural features and historical significance. It is recognized on UNESCO's tentative list of World Cultural Heritage sites as part of Brazil's defensive fortress ensemble.
