The works for the construction of the Fortress and the arrival of the first troop on 1630 suggest that the old "Casarão" could have other funtion different to residence. Taking account of the place goemetry, and the place where it was built, "O Casarão" seems to have been an integrated part in the structure of the fortress, the Portalo (gateway), ramp, and finally the buildings on the second hill, overlooking the
Praca Aureliano Lima as well

as the entire area between the landing bridge and the second beach.
Some records indicate that during the construction of the fortress, as well as after its completion, the houses along the road leading from the square to the first beach were used to house the soldiers of the garnison, while, quite assumably, higher ranking personell were lodged in the Casarao.