The Fortress of São Marcelo is a historic military fort located in Bahia, Brazil. Built in the 17th century, it was designed to protect the city from naval attacks and pirates. The fortress is situated on a small island in Baía de Todos os Santos, making it a strategic defensive position. Constructed in a circular shape, the fortress features thick stone walls and a central courtyard. Over the years, it has served various purposes, including as a prison and a military base. Today, the Fortress of São Marcelo is a popular tourist attraction, showcasing its rich history and stunning views of the surrounding bay.