The Fort of São Julião da Barra is a historic military fortress located in Cascais, Portugal. Built in the 16th century, it was designed to protect the entrance to the Tagus River and the city of Lisbon from naval attacks. The fort features a mix of Renaissance and Manueline architectural styles, showcasing its strategic importance during various conflicts. Over the years, the fort has served multiple purposes, including a military barracks and a prison. Today, it is a popular tourist attraction, offering visitors a glimpse into Portugal's maritime history and stunning views of the surrounding coastline and the Atlantic Ocean.