It has always existed in the imaginations of those who know the legends of Cartagena, a slave-trading port on the Caribbean Sea, seat of the Inquisition in the New World, and fortress colony coveted by pirates for its Spanish gold. Constructed on a sand bank at the entrance to the Bay of Cartagena, the Fort of San Matías was connected to the mainland by a submerged barricade that would lacerate enemy ships before being attacked from the nearby batteries.
Flanked by the eastern ridge of Tierra Bomba – a large island near to Cartagena – the Fort of San Matías resisted the onslaught of privateers, the Royal Navy and history, only to resurface, as a significant archaeological discovery for Colombia. Tierra Bomba is located between two channels, the relatively shallow channel Bocagrande, and to the south by the smaller and deeper Bocachica.
Despite its strategic role in the defense of the city and gateway to the New World, the Fort of San Matías was dismantled in 1626, leaving only vague references in colonial maps and chronicles. For centuries, historians and archaeologists had searched for its remains in vain. But in 2014, a team of researchers from the Colombian Maritime Directorate (Dimar), led by Richard Guzmán, Diana Quintana, and Carlos Andrade, embarked on an ambitious mission to map the region’s submerged cultural heritage.
What began as a study of the Bocagrande breakwater – known as La Escollera – revealed a promising lead. Using cutting-edge three-dimensional acoustic sonar technology, the team mapped the sea floor, uncovering unexpected anomalies. What appeared to be a perfect geometric formation was not a shipwreck, as initially suspected, but a manmade structure, with angles too precise to be naturally occurring. Further investigations, including comparisons with colonial-era maps, confirmed that the structure was, indeed, the long-lost Fort of San Matías.
Measuring more than 80 meters in length, the fort’s remnants lie at a depth of six meters below the surface of the Bocagrande Bay. It is a poignant reminder of Cartagena’s once formidable defenses, designed to protect the city from frequent attacks by pirates and rival European powers. As the city’s primary defense against threats from the sea, San Matías was an essential part of the fortification system that also included the larger San Fernando and San José forts, which were strategically positioned to create a multi-layered defense.
The rediscovery of San Matías is significant not only for its historical value but also for its potential to deepen our understanding of Cartagena’s colonial past. The fort’s location at the mouth of Bocagrande Bay underscores the strategic importance of the territory, which was repeatedly besieged by English, French, and Dutch naval forces.
Its existence offers new perspectives on the scale and ambition of Spanish military engineering in the Caribbean during the colonial period. Construction of the Bocagrande Breakwater was ordered by the Crown on 15 October 1764. The project was entrusted to Antonio de Arebalo, a mathematician and military engineer appointed to design, direct and complete the fortification.
According to the authors of the survey titled ‘”La Escollera” and a Submerged Structure Related to Fort San Matías in the Bay of Cartagena de Indias’, the fort was dismantled in 1626, as the Spanish Crown shifted focus to more modern fortifications such as the Fort of Santacruz de Castillogrande, located further inside the Bay.
Over time, natural forces – storm surges, hurricanes, and the relentless erosion of the coastline—conspired to erase all physical traces of the fort, leaving only faint records in old maps and documents. By the time urban development transformed the coastline in the 20th century, San Matías had become little more than a footnote in the city’s history.
Diana Quintana, one of the lead researchers, emphasized the importance of the discovery not just for archaeology but for public engagement with the history of Cartagena. “This site represents more than just bricks and mortar,” she explained. “It is a symbol of the city’s resilience and its ongoing efforts to preserve its cultural heritage. Protecting these submerged structures is a delicate balance between scientific exploration and environmental stewardship.”
The challenges of preserving submerged heritage sites are not insignificant. The waters surrounding Cartagena are home to a rich array of marine life, and the fort’s location within a busy urban bay makes it vulnerable to damage from human activity. However, the team’s findings have sparked a renewed commitment to monitoring and protecting Cartagena’s underwater cultural resources, ensuring that this chapter of the city’s history remains intact for future generations.
While the discovery of the Fort of San Matías is a major achievement for Colombian archaeology, it also shows the vast potential for future discoveries in Cartagena’s waters. The city is already famous for its colonial fortifications, which were designated a UNESCO World Heritage site in 1984. Yet, this recent find serves as a reminder that much of the city’s maritime heritage remains hidden beneath the surface, waiting to be uncovered.
The search for Cartagena’s lost fortresses is not over. In fact, researchers are already considering further exploration of the Bocagrande Bay and surrounding areas. Other colonial structures, such as the Fort of San Luis in Bocachica and the Santángel Batteries, are believed to lie submerged, their precise locations still shrouded in mystery.
The rediscovery of the Fort of San Matías opens a new chapter in the ongoing narrative of Cartagena – a city that, through its layers of history, has borne witness to the ebb and flow of empires, the clash of cultures, and the unrelenting forces of nature. The fort may have been abandoned, its walls crumbling under the weight of time, but beneath the waters of Cartagena Bay, it has found new life as a symbol of the city’s enduring legacy and a treasure trove for future generations of historians, archaeologists, and explorers.
