The Lighthouse of Alexandria rose in the early 3rd century BCE and, for 1,600 years, it withstood earthquakes, storms, and the passage of time until, little by little, it disappeared beneath the waters of the Mediterranean. Now, what was once one of the Seven Wonders of the Ancient World is starring in an unexpected comeback thanks to a combination of underwater archaeology, advanced engineering, and technology.
And the international PHAROS project has just recovered 22 enormous blocks belonging to the original structure. Some of these pieces weigh between 70 and 80 tons, so the operation has been closer to industrial salvage than to traditional brush-and-brush archaeology.
The same technology that designs cars and airplanes to solve a mystery dating back 2,300 years
Among the elements rescued by the Franco-Egyptian team led by archaeologist Isabelle Hairy, from the French CNRS, are lintels, jambs, thresholds and large granite slabs that formed part of the lighthouse’s monumental entrance. The archaeologists aim to use them to solve a centuries-old incomplete puzzle: digitally reconstruct one of the greatest engineering works of Antiquity and discover how it managed to stand for more than a millennium.
To achieve this, the engineers will not limit themselves to producing renders, but will employ tools for product lifecycle management and advanced three-dimensional simulation… using the same type of software that automotive brands use to run structural stress tests on the chassis of high-performance cars or to calculate the aerodynamics of airplanes before building a physical prototype.
Involving this level of reverse engineering will allow a deep analysis of the incredible work of Sostratus of Cnidus, the Greek architect who, under the reign of the early Ptolemies, raised the lighthouse, nearly 100 meters tall. That infrastructure, the tallest in the world for centuries, proved essential for the safety and trade of the Mediterranean by centralizing the maritime traffic that arrived at the port of Alexandria.
The digital twin against seismic challenges
However, the key of the project does not lie in the blocks recovered now, or in the more than a hundred architectural elements that had already been digitized on the seabed over the last decade, but in what will be done with them: each piece will be scanned using high-precision photogrammetry to generate exact three-dimensional models.
From here, engineers at the Dassault Systèmes Foundation will build a complete digital twin of the monument, and thanks to that virtual reconstruction the researchers hope to answer some of the great unknowns surrounding the lighthouse. Among them, how a structure of such scale managed to stand for around 1,600 years in a region especially exposed to tectonic movements.
At present, some hypotheses point to the key being the use of molten lead in the joints of the blocks to absorb shock waves and impart a certain flexibility to the whole. If confirmed, archaeology would be documenting the direct ancestor of modern seismic isolators and elastomers that civil engineering now installs on bridge piers and skyscraper foundations so that they can deform without collapsing.
A wonder that was also a logistics machine
The Lighthouse of Alexandria was not only a spectacular monument ahead of its time, but also functioned as critical infrastructure for navigation and trade in Antiquity. Keeping its light visible tens of kilometers away required a complex supply chain capable of transporting fuel consistently to the top of the tower.
Various investigations point to the existence of a huge interior helicoidal ramp through which mules and donkeys ascended loaded with wood, resins, and above all, charcoal. From the upper terraces, pulley and winch systems completed the vertical transport of the cargo to the combustion chamber, forming a design so sophisticated that many experts consider it one of the great civil engineering works of the ancient world.
The choice of charcoal responded to a strict criterion of energy efficiency and logistics: by offering a calorific value far superior to that of green wood, it dramatically reduced the volume of cargo and the number of trips needed daily. In addition, it guaranteed a clean and soot-free combustion, a critical factor to prevent the black smoke from obscuring the large bronze-polished mirrors that multiplied the light’s reach in the distance.
The significance of the PHAROS project goes beyond the lighthouse itself, because if the digital reconstruction succeeds, this same methodology could be applied to submerged Roman ports, vanished cities beneath the sea, or historical shipwrecks scattered around the globe. The current campaign is demonstrating that some of the great engineering feats in history can still reveal their secrets thanks to 21st-century technology.
Images | National Geographic, GEDEON Programmes
