It has a star form. Its measures 250 by 300 meters. The slightly inclined, massive walls are 8 meters high on average, with thickness of 10m enclosing a patrolling peripheral walkway 2m wide. Four bastions surrounded the fortress: Angel Bastion from east, Saint Sebastian in the north, Saint Antoine in the west, in the south the Holy Ghost Bastion, the fifth one is the Governor’s Bastion at the main entrance is in ruins. Having been destroyed by Portuguese, colonial era Portuguese cannons are still positioned on the top of the bastions. The fort has three gates: Seagate forming a small part with north east rampart. The Bull gate in the North West rampart. The main entrance with a double arch in the centre of south rampart originally connected to land via a drawbridge. A ditch, 20 meters wide and 3 meters deep. Formerly filled with seawater, surrounded the fort. During the time of French protectorate the ditch was felled with earth and a new entrance gate was opened leading to the main street. The Rua Carreira and the Sea gate.
The Portuguese Cistern, built in 1514, is an underground chamber of 34 meters by 34m which was constructed with 5 rows of 5 stone pillars. The cistern is famous for the thin layer of water that covers the floor and which creates fine and exciting reflex ions from the little light there and the Spartan shapes of the columns and the roof. Several movies have been filmed within the cavernous space of which Orson Wells Othello is the best known internationally.