This Knights' period powder magazine complex was built in 1756 as commemorated in a marble inscription above the doorway.

The polverista was built in the innermost part of the Grand Harbour at the coast's edge at Ras Hanzir, in the Marsa area, so that it could be supplied by boat and it was built close yet sufficiently away from the fortified settlements for safety purposes.

The complex originally consisted of two parallel, very large vaulted stores with double pitched roofs and pointed stone arches, an identical smaller store, and a smaller vaulted room which were interconnected. The magazines are surrounded by a thick high wall for security and also to contain any explosion of the stores. Access to the complex was restricted by a single central gate.

The exterior walls have flanking buttressed arches at intervals to withstand the lateral thrust of the arched vaults.

The stores were built with an elevated floor forming a basement to prevent dampness. A central courtyard served as a buffer between the stores and to ventilate the magazines.

During the British period these magazines were subjected to a number of adaptations.

The central courtyard and the garde de feu were roofed over, with the former serving as ablutions. The central courtyard was divided into a number of equally spaced divisions by means of thick, segmental stone arches, each having a large ventilator in the ceiling.

Between each arch, other divisionary walls were erected and the whole was roofed over by wooden beams and stone slabs (xorok). Natural light entered through windows in the outer wall which probably doubled as musketry embrasures for defence if required. Indications in support of the assumption that the British had converted the magazines into a small fortified barracks result from the way the new roof over the courtyard was constructed. The roof is sunk behind the outer wall to a depth of a man's height providing a protected position for soldiers to fire from. Mepa scheduled Ras Hanzir Polverista as a Grade 1 national monument and ancillary structures as Grade 2 national monuments as per Government Notice no. 628/08 in the Government Gazette dated July 21, 2008.