– credit, GEDEON Programmes / CEAlex
22 massive granite blocks that once formed the Great Lighthouse of the Alexandria have been hauled up from the bottom of city’s ancient harbor.
The blocks weighed dozens of tons each and consisted of upright pillars, frames, and crossbeams called lintels that once formed the entrance to the structure.
Called one of the 7 Wonders of the Ancient World by the Greeks of the time, a series of earthquakes in the 10th century CE and later sent the famous lighthouse crumbling into the harbor.
France’s National Center for Scientific Research (CNRS) and Egypt’s Center for the Studies of Alexandria (CEAlex) led a project to map and study the blocks and other remnants scattered across the seabed. Ongoing for over a decade, a landmark 2014 analysis identified some 3,000 blocks and another 5,000 stone pieces of the lighthouse scattered across a 4 acre area.
Every block that came up was thoroughly photographed, with the results channeled into a photogrammetry database where researchers could return and study each block with precise 3-dimensional detail in the lab.
With many of the blocks thusly analyzed, the CNRS team, led by Isabelle Hairy, began to hypothetically reassemble the ancient monument block by block. Sophisticated digital modeling software allowed them to test how certain blocks would fit together at the click of a mouse rather than the groan of a crane. The precise 3D-renders included things like rough and fine edges, chips, and tool marks that informed the potential placements.
Earth.com reports that when two segments seemed to fit, they could also run simulations to see what characteristics an earthquake might have had, in terms of intensity and direction, to crack and topple it.
– credit, GEDEON Programmes / CEAlex
Built when an august general under Alexander of Macedon named Ptolemy decided to make himself ruler of Egypt after the former’s empire was carved up following his death, the lighthouse guided ships into the harbor of Alexandria for centuries, and was built so soundly that it took multiple earthquakes over several hundred years to eventually destroy it.
Ibn Jubayir, a Moorish pilgrim on route to Mecca, attempted description of the lighthouse, but couldn’t wrap his head around exactly where to start.
It is most strongly built in all directions and competes with the skies in height. Description of it falls short, the eyes fail to comprehend it, and words are inadequate, so vast is the spectacle. We measured one of its four sides and found it to be more then fifty arms’ lengths. It is said that in height it is more than one hundred and fifty. Its interior is an awe-inspiring sight in its amplitude, with stairways and entrances and numerous apartments, so that he who penetrates and wanders through its passages may be lost. In short, words fail to find a conception of it.
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Several of the blocks bore Egyptian imagery and iconography, even though they were carved with Hellenistic techniques, capturing the synthesis of cultures under the Ptolemaic dynasty. At the same time, however, the CNRS team believes that some of the granite monoliths came from an Old Kingdom site at Abu Rawash, which would predate the lighthouse by 2,000 years at least.
As tantalizing as it is to imagine reassembling at least part of the structure, Egyptian authorities do not permit the recovery of any blocks over 220 pounds. After so many years immersed in salt water, exposure to oxygen risks irreparable damage to the larger stones coming from salt crystals growing in size in the cracks and crevices while drying out.
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After photographing, the largest elements were returned to their watery beds.
The 3D model that has been constructed could, the researchers suggest, lead to novel ways of interpreting and presenting the nature of the monument to visitors. With a precise idea of how the lighthouse was built and the stones stacked, one can imagine, perhaps given another decade, a holographic projection of the structure rising above the harbor at Alexandria just as its name sake had done for more than a millennia.
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