The S. João das Maias Fortress is located on the right bank of the Tagus River near its mouth, between Santo Amaro de Oeiras Beach and Paço de Arcos Beach in Oeiras, Portugal. The S. João das Maias Fortress is a construction of the century XVII, begun in 1644 and completed in 1653, with a pentagonal shape and for purpose the reinforcement the coastal defense after the Portugal Restoration Independence. The fort was restored in the 1st half of 2010, there is now framed in harmonious surroundings.