Lighthouse of Alexandria: Huge Architectural Fragments Recovered from the Sea

Off the coast of Alexandria, underwater archaeologists have recovered huge architectural fragments believed to belong to the city’s renowned ancient lighthouse. The discoveries were made at a depth where debris from the former wonder of the world has lain for centuries. The material now provides tangible evidence of what this iconic structure actually looked like – and why it ultimately disappeared.

Spectacular recovery from the floor of Alexandria’s harbour

For years, diving teams and archaeologists have been working in the shallow coastal waters off the modern city of Alexandria, home to millions of people. Remains of the ancient city lie there after earthquakes and coastal subsidence caused them to slip beneath the sea. During the latest expedition, researchers lifted 22 enormous structural elements from the seabed into the harbour.

The recovered pieces include a monumental gateway weighing up to 80 tonnes and a vast pillar interpreted as part of the lighthouse.

Blocks of this scale demonstrate the extraordinary magnitude of the ancient structure. Roman writers had already described the Lighthouse of Alexandria as an immense building that was almost without equal. Until now, research had relied chiefly on written accounts, historic depictions and scattered underwater discoveries. The newly recovered sections are far better preserved and can be measured directly.

The operation on the seabed follows a strict procedure. Divers first record every fragment using underwater cameras, before attaching lifting bags or specially designed frames. A crane aboard a support vessel then raises the blocks from the water. Once ashore, they undergo photography, laser scanning and analysis of the building stone inclusions.

What made the Lighthouse of Alexandria so exceptional

The lighthouse was built around 280 BC during the reign of Ptolemy II. It stood on the small island of Pharos, just offshore from Alexandria’s harbour. From there, its light guided ships into one of the Mediterranean world’s most important trading ports.

Ancient writers were already amazed by both the scale and technical sophistication of the building. Its height is generally estimated at more than 100 metres, making the tower effectively a high-rise building of the ancient world. It was counted among the “Seven Wonders of the World” because it combined a practical function with a prestige project and a symbol of scientific progress.

Lighthouse of Alexandria architecture across three levels

Researchers assume that the structure was divided into three parts:

• Substantial base: a square lower section designed to withstand waves and serve as a platform
• Octagonal middle section: a lighter-looking tower element that increased the overall height
• Cylindrical summit: the upper part of the tower, containing either a fire or a mirror apparatus

Whether its light was produced by an open flame or intensified through sophisticated mirror and lens systems remains a subject of debate. What is clear is that the tower could be seen far out at sea and shaped the appearance of the coastline for many centuries.

Several powerful earthquakes damaged the building during the Middle Ages. Accounts in Arabic sources describe the tower, in some cases, as a ruin already. By the beginning of the 15th century at the latest, it had collapsed. Builders later reused its stone in harbour fortifications, while many blocks slid directly into the sea.

From a field of rubble to a digital model

The elements now recovered are central to a research project called “Pharos”. Led by architect and building researcher Isabelle Hairy, the team aims to reconstruct the lighthouse’s structure virtually.

Every stone block is recorded using 3D technology and inserted into an overall digital model like a puzzle piece.

Millions of measurement points create a precise dataset. Researchers can simulate different versions of the tower, varying its height, wall thickness and internal stairways. This allows them to test which version is structurally plausible and consistent with historical descriptions.

This creates the basis for new questions:

• How severely did earthquake loads affect the tower?
• At which weak points did the structure fail first?
• Which Hellenistic construction methods are present in the masonry?

There are high expectations for the analysis of fracture surfaces and weathering traces. These may reveal clues about the blocks’ original positions. If, for example, a pillar is heavily eroded on just one side, that side may once have faced the open sea.

Underwater archaeology among sand, currents and modern activity

Working off Alexandria is far removed from the romantic image of wreck diving. Visibility varies, harbour traffic creates currents, and sediment is constantly deposited in new places. Simply locating rubble fragments that can be clearly identified demands considerable patience.

Modern technology makes the work easier: sonar maps the seabed, drones provide aerial imagery, and specialist software overlays all available data. A broader plan of the ancient harbour area is gradually emerging. Within it, the lighthouse was not merely a landmark but part of a complex network of moles, warehouses and temples.

Why Egypt yields so many discoveries

Egypt has long been regarded as an archaeological treasure trove. Alongside pyramids and burial sites, underwater locations have increasingly become the focus of attention in recent years. Sunken cities in the Nile Delta, former trading centres in the Red Sea and military installations all significantly broaden our understanding of the country’s history.

The latest recovery fits this wider picture. It shows that many famous structures can be reconstructed not only from texts and reliefs, but also from actual components that survive at their original scale. For engineers and structural specialists, this offers rare direct access to ancient building practice.

What visitors may one day be able to see

The project team intends to present the digital reconstruction to more than just specialist audiences. Virtual tours are being considered, allowing interested visitors to experience the lighthouse in real time on a screen or through VR headsets. They could move from the harbour quay to the summit, climb the stairs and look out across ancient Alexandria.

Exhibitions in museums in Egypt and Europe are also possible. These could combine original blocks, scale models, projections and interactive displays. A possible visitor route could include:

• An introduction featuring an animated view of the ancient harbour
• A display of original stones with an explanation of their recovery
• A VR area offering a virtual ascent of the tower
• A section on modern underwater archaeology and its methods

Such formats make clear just how much work is required to turn seemingly shapeless masses of stone back into a recognisable building – at least in the digital realm.

Terms and background for a clearer understanding

The term “wonder of the world” goes back to ancient writers who singled out seven remarkable buildings and landscapes. Alongside the Lighthouse of Alexandria, these included the Pyramids of Giza and the Colossus of Rhodes. Many of these monuments have long since vanished, which makes their reconstruction particularly compelling.

Virtual archaeology uses modern technologies such as 3D laser scanners, drones, photogrammetry and physical simulations. A digital copy does not replace the discovery itself, but it provides a kind of laboratory in which historical hypotheses can be tested safely. If a virtual model repeatedly cracks at the same point under earthquake loads, for example, this can indicate genuine weaknesses in the historic structure.

Research into coastal cities involves a further consideration: many ancient places now lie underwater because coastlines have shifted. Anyone studying these cities must bring together geology, marine science and archaeology. The Lighthouse of Alexandria is an especially visible example of this, but it is far from the only one.