Next to Barra Beach there is the Fort of Barra, one of the two that used to protect the city. The fort is open to visitors, who have to pay a small fee.
To get back to the center from Barra, you can take a taxi or one of the air conditioned buses (direction Sé Square). On the way you will ride along one of the busiest commercial avenues in town, Avenue 7 de Setembro. If you have some time left, you can get off at Praça Piedade, and visit a couple of interesting buildings.