The ongoing restoration of Old Willis’s Magazine, commonly known as the City Under Siege exhibition, has led to the identification of an 18th-century defensive tower, once forming an integral part of the magazine’s southern defences.

The team at Wright Tech Ltd, working in partnership with restoration specialist and project curator Manuel Jaén, located the structure through detailed historical and cartographic research, analysing plans dating back to the Great Siege of Gibraltar (1779–1783) and correlating them with later WWII military maps. This meticulous study was supported by the identification of a rare 19th century photograph, which clearly depicts the tower before its destruction or dismantling, confirming that the structure once extended the known defensive limits of the City Under Siege Complex. 

Situated beyond the southern magazine and overlooking a steep cliff face, the tower served as a watchtower and defensive outpost, protecting the powder magazines from possible attacks approaching from below. The area also contained a fortified corridor (Coracha), designed to shield movement between the magazine and an external water well, combining both logistical and defensive purposes. 

During the current conservation phase, cleaning of the southern sector revealed the tower’s remaining foundations, hidden beneath decades of accumulated debris and vegetation. Of particular importance was the identification of a machicolation, a defensive feature built directly into the base of the tower. This architectural element, unique in Gibraltar, consisted of a mortarlined shaft projecting from the wall, enabling defenders to drop grenades or other projectiles onto enemy forces attempting to scale the cliffs below. The machicolation extended outward through a smooth, lined channel, designed to ensure precision when releasing munitions down the slope. 

The presence of this feature redefines the historic understanding of the Old Willis’s Magazine complex, expanding its role from a passive ammunition storage site to that of an active defensive fortification. Though the machicolation is a design rooted in medieval fortifications, its adaptation within this 18th-century structure reflects a neo-medieval defensive revival typical of the period, maintaining traditional defensive tactics even in the age of gunpowder and artillery. 

The re-discovery has been brought to the notice of the Gibraltar National Museum. 

Christian Wright, Local Historian and Managing Director at Wright Tech, said: “Through careful research and restoration, we are not only conserving a site, we are uncovering how Gibraltar’s defenders thought, built, and adapted across centuries. The identification of this tower and its machicolation demonstrates that our heritage still holds surprises, and that with every step, we are rewriting the story of Gibraltar’s fortifications.” 

Dominic Lopez, Government Archaeologist said: “The identification of this defensive tower within the City Under Siege Complex marks an extraordinary addition to Gibraltar’s military heritage. The machicolation - a feature used to defend the cliff base by launching projectiles at attackers - highlights the ingenuity of Gibraltar’s fortifications and their evolution through time. This structure not only expands our understanding of the site’s defensive role but also connects Gibraltar’s military history with broader European traditions of fortification design” 

Restoration Expert and Project Curator, Manuel Jaén said: “Our conservation work ensures the preservation and restoration of newly discovered elements that enrich Gibraltar’s heritage, while protecting the site’s structural stability with the utmost scientific rigor. Recent additions that distort the original perception are being removed, respecting the authenticity, construction phases, and passage of time to offer visitors a clear and accurate interpretation. All work follows international conservation principles, using reversible and compatible materials, distinguishing original areas from those treated, respecting historical traces, and applying conservation criteria that avoid any form of reconstruction.” 

Director of the Gibraltar National Museum Prof Clive Finlayson said, “It is always exciting when new structures are discovered, or when the extent of those we knew existed is shown to be greater than expected. Here we have yet another addition to our rich heritage and I commend the operators of the site for their enthusiasm, which has led to this rediscovery.” 

Minister for Heritage Prof John Cortes said: “This is a really exciting find. The amount of work that is being done on heritage sites in Gibraltar is unprecedented, and is bound to turn up unexpected gems such as this one.  There are still many gaps to be filled in our knowledge of our history throughout all of Gibraltar’s successive periods, and the best way to fill these is by active research on the ground.” 

Plans are now being adapted to ensure that the tower and its machicolation are incorporated into the site’s interpretation, with controlled public access under consideration in future phases. The project will continue to prioritise research-led conservation, balancing scientific accuracy, public education, and long-term preservation.