Fort Manoel at Marsamxett Harbour was constructed as part of the 18th century harbour defence system to protect the west side of the Valletta landfront. The original construction included two polveristas (or powder magazines) built on the seaward bastions, with construction set to begin after January 1727. The deadline for the different works was established in the contract for works with construction (completion) of the polveristas taking place in 1729. Unfortunately only one of the magazines survived.

The original contract required the limestone to be quarried from the excavation of the Fort Manoel ditch and 'to be of the best quality'. The structure was rendered bomb-proof through a solid construction and the structure was reinforced by counterforts, or rather, five buttresses on either of the longer sides, with the roofing system consisting of a barrel vault beneath a gabled roof.

To restrict access to the magazines, blast walls or couvres de feu, of which only a small portion exists, were built to 'seal off' the area; these were constructed between the intersection of the curtain and bastion walls.

Narrow openings or ventilation shafts, described as sfiatatori, were required to allow air inside the magazine; the wall sections between the buttresses supposedly contained four such vents.

Considering the use of the polverista, it was imperative to keep the structures as dry as possible, and reference is made to this in the original documents. In fact, a series of ventilating channels beneath the internal flooring and a portion of the external areas were unearthed during restoration works.

The polverista that survives, and which has been restored, consists of a single rectangular room, of circa 124 metres square and is located on St Helen's Bastion; the other, constructed on St Anthony's Bastion, was demolished by the British military in 1872 as part of the upgrading of the defences of the fort to meet defence artillery standards of the time.

The restoration of the polverista and its immediate environs was one of the first phases carried out as part of the restoration of 18th century Baroque Fort Manoel. Emergency works began between 2001 and 2002 to prevent further collapse of the structures in the fort. In 2004, the first phase of restoration works commenced - this included the polverista.

As the only surviving polverista at Fort Manoel, it was necessary to ensure that all features of the structure be understood and carefully protected and/or restored. The different elements were studied in detail to ensure that all parts were identified, adequately protected, restored or conserved. The aim was to restore the built fabric with its immediate environs (enclosed by and including the 'blast wall').

The main interventions primarily involved the demolition of historically unimportant accretions, removal of debris, repair of the globigerina limestone, removal of vegetation, repairs to the damage by warfare and years of neglect and vandalism. Restoration works also included the singular gabled roofing structure, which was repaired and reinstated where severely damaged.

By now a better understanding of the site could be acquired, particularly after unearthing buried structures, such as a retired platform and flooring ventilation system, of which there was no evidence before works started. These 'unforeseen circumstances' also meant that new reports were formulated accordingly and changes to the original envisaged works instructed.

The design of the restoration intervention has also included the reinstatement and/or reintroduction, of the original floor levels, along with the restoration of all known developments relevant to the military history of the area.

The materials used for the interventions were 'traditional' materials, as originally employed in the construction of the fort, but designed and interpreted in a contemporary way to make it recognisable.

The polverista over St Helen's Bastion is now more easily interpreted, with the overall image of the restored polverista and its immediate environs being aimed at conveying a complete understanding of its multi-faceted past, as part of the 'military machine' through the exposure of the different important layers of its history.

This is the third of a series of articles written by Professor Alex Torpiano, and architects Konrad Buhagiar, Svetlana Sammut and David Zahra - aoM Partnership - which aims to focus on the restoration works undertaken by Midi plc as part of the Manoel Island and Tigné Point development project.