The Lighthouse of Alexandria, erected in the 3rd century BCE on the island of Pharos, was far more than a simple guide for sailors. Regarded as one of the Seven Wonders of the Ancient World, this stone colossus dominated the eastern Mediterranean and embodied an outstanding feat of engineering.

The underwater archaeological excavations, conducted since 1994 by the Centre d’Études Alexandrines (https://pharos.cealex.org/les-fouilles-archeologiques/) and supported by the Honor Frost Foundation (https://honorfrostfoundation.org/), have uncovered an invaluable treasure: thousands of exogenous rock blocks (granite, quartzite, marble, diorite, etc.), including major architectural elements such as the monumental gateway, foundation stones, frieze, cornice, large slabs, and vault voussoirs.

These remains revealed the builders’ resourcefulness, especially through the discovery of numerous metallic elements, clamps and dowels made of lead, iron and bronze, demonstrating an advanced mastery of metallurgy and a resolve to ensure durability in the face of traumatic events (storms, earthquakes, wars, etc.).

Indeed, the Lighthouse of Alexandria operated for nearly 16 centuries, weathering major historical events, storms, and no fewer than 18 earthquakes and tsunamis. Yet a devastating earthquake in 1303 marked the beginning of its decline. The pressure of subsidence and coastal erosion, together with eight further earthquakes, would cut short restoration attempts; the monument eventually collapsed. In 1435, its ruins were noted once more before being swallowed by the waters.

The underwater remains, though precious, account for only 7,000 tonnes of stone, i.e. less than 10% of the original construction, and some blocks even belong to other buildings. To bridge these gaps, the Pharos project was launched in 2023, the product of collaboration between CEAlex and the Fondation Dassault Systèmes (https://www.lafondation3ds.org/fr/). This ambitious project aims to reconstruct the Lighthouse of Alexandria virtually.