its initial purpose was to repel attacks by the french who ambitioned to hold a possession in the then colony of brazil and tried to destabilize it with harassing incursions along the shore - after several episodes of disbandonment and activation, it remained as an operational fortress until 1991 when it was converted to take on a more educational role - in fact, it is currently the home of the museum of army sports and three military research institutes.

the fort is open to the public tuesday through sunday, between 10 am and noon - and entrance is free of charge - special authorization to visit the fort's beaches praia de dentro and the nearby  praia de fora can be requested  in person at the fortaleza de são joão - an authorization can also be requested via email  here.