The Forte Real de São Filipe was built in 1587, in a dominant position of about 120 meters above sea level, it was the first and most important fortification of the archipelago. It headed the city's defensive system, made up of six more small fortes scattered at various strategic points in the Cidade Velha.
In architectural terms, we can see that the royal fortress of São Filipe has a polygonal plan with a bastioned layout with two facades facing the campaign and two walled fronts with parapets, facing the center of the city. It has a bastion in the center facing east and two half bastions with payphones at the opposite ends of the curtains. The other two sides of the quadrangle where the fortress is inscribed follow the course of the step land.