Almost everyone has heard of the Pharos at Alexandria – one of the Seven Wonders of the Ancient World. There is no question about its existence, but we are still not entirely sure of the years when it was built. The best estimate is that it was constructed sometime after the death of Alexander the Great in 323 BC. Its great size would have meant that it took possibly twenty years to construct. It is fairly certain to have been completed by 270 BC. Many authors believe it was started around 290 BC. Zemke  reports that it took 17 years to build from 300-283 BC; Stevenson quotes 280 BC for its completion.
The city of Alexandria was still new when the building of the Pharos began. The death of Alexander the Great gave Emperor Ptolemy a new financial, as well as political, freedom. Released from the obligation to send taxes to Byzantium, he embarked upon a spending spree, expanding his new city with vigour. He decided upon a massive new project to build a lighthouse and commissioned an architect called Sostratus to design it. The lighthouse was to be built on an island in the Bay of Alexandria and linked to the shore by a narrow isthmus.
Ptolemy instructed Sostratus to ensure that the name of Ptolemy was in a position of prominence. Thus, the people of succeeding generations could marvel at the vision and power of this great king. Sostratus, however, decided that his own contribution should not go unrecognised. He instructed the masons to carve his own name into the stone and to cover it in soft cement that he knew would weather away over a short number of years. Ptolemy’s name was added to the soft cement...
Whether the lighthouse was called Pharos because of the name of the island on which it was built, or whether the name of the island arose because of the Pharos being built there is a matter of debate. Pharos was the Greek word for lighthouse, but we have no precise knowledge of its entry into the language. Some writers argue that the word pharos arose because the lighthouse was built on an island with the pre-existing name of ‘Pharos’. This argument is tenable only if no lighthouses of any kind had existed previously. This paper argues that lightstructures had been in existence for a thousand years so, at the time of the building of the Pharos, the existing Greek word was applied to it and the island on which it stood. The word exists today in French as ‘phare’, and Spanish, Italian and Portuguese as ‘faro’.
Because of its fame and longevity, the Pharos of Alexandria became the model for many lighthouses thereafter. Over many centuries, it has been written about more than any other lighthouse and, for obvious reasons, a great deal of inconsistency has developed as to its actual design. There are many illustrations, which vary enormously in their portrayal of the structure. For example, the thirteenth-century mosaic in the Zen Chapel of St Mark's, Venice, purports to show the Pharos of Alexandria as a backcloth to an episode in the life of St Mark, but probably does not accurately represent the real structure.
‘Modern’ interpretations allow us to reach reliable conclusions as to its size and shape. In fact, they bear a remarkable similarity to those of an Arabian observer of 1165, who Stevenson describes as ‘reliable’. He took detailed measurements and described a building of three storeys, the bottom being square in section, the middle octagonal and the top circular. The base of the tower was colonnaded, 110 m square and 7 m above water level. The lower section of the main body of the tower was 30 m square and 72 m high; the middle section octagonal, 17 m across and 35 m high; the top section cylindrical, 9 m diameter and 26 m high. The geographer, Edrisi, who visited the tower about 1150, before its destruction, described how the stones were strapped together by metal ties and declared that it was reduced in diameter as it rose upwards until at the top its pinnacle could be clasped by a man's arms. The stairs were well-lighted by windows.
A lantern graced the summit. Whether it was glazed or open to the weather is not known, but it is likely that it was not glazed. Without further comment or support, and referring to lighthouses generally, Stevenson baldly states, “Glass panes were used after the 1st century A.D.” In the 16th and 17th centuries, lighthouses lit by fire faced real difficulties in this regard because soot coated the inside of the panes of glass and there were problems in dealing with huge amounts of smoke. All this greatly reduced visibility at sea. Thus, it is most likely that the lantern, whilst covered with a roof, was nevertheless open to the atmosphere. Indeed, a statue of Poseidon is believed to have featured on top of the building and that the total height of the Pharos was over 140 m, exceeded only by the Great Pyramid of Cheops . No other lighthouse has ever been built as tall as this. In recent times the closest competitors are Lanterna in Genoa, Italy, which is 57 m and Ile Vierge in Finistere, France, which is 82 m.