At the mouth of the Tagus River, the São Julião da Barra Fort was built in the second half of the 16th century as a reinforcement of the city’s defenses and was regarded as the “Shield of the Kingdom.” In addition to the military mission of defense, it worked as a college of education, as a prison, and from 1951 is used in representation of acts of the National Defense agencies, and more recently as the residence of the Minister of National Defense, as well as a space for private functions.