Sostratus, the son of Dexiphanes, the Cnidian, dedicated this to the Saviour Gods, on behalf of those who sail the seas.
Dedicatory inscription of the Lighthouse

Of the Seven Wonders of the Ancient World, only one had a practical use in addition to its architectural elegance: The Lighthouse of Alexandria. For sailors, it ensured a safe return to the Great Harbor. For architects, it meant even more: it was the tallest building on Earth. And for scientists, it was the mysterious mirror that fascinated them most... The mirror which reflection could be seen more than 50 km (35 miles) off-shore.

Location
On the ancient island of Pharos, now a promontory within the city of Alexandria in Egypt.

History
Shortly after the death of Alexander the Great, his commander Ptolemy Soter assumed power in Egypt. He had witnessed the founding of Alexandria, and established his capital there. Off of the city's coast lies a small island: Pharos. Its name, legend says, is a variation of Pharaoh's Island, but it is more likely that the name is Greek in origin. The island was connected to the mainland by means of a dike - the Heptastadion - which gave the city a double harbor. And because of dangerous sailing conditions and flat coastline in the region, the construction of a lighthouse was necessary.

The project was conceived and initiated by Ptolemy Soter around 290 BC, but was completed after his death, during the reign of his son Ptolemy Philadelphus. Sostratus, a contemporary of Euclid, was the architect, but detailed calculations for the structure and its accessories were carried out at the Alexandria Library/Mouseion. The monument was dedicated to the Savior Gods: Ptolemy Soter (lit. savior) and his wife Berenice. For centuries, the Lighthouse of Alexandria (occasionally referred to as the Pharos Lighthouse) was used to mark the harbor, using fire at night and reflecting sun rays during the day. It was even shown on Roman coins, just as famous monuments are depicted on currency today.

When the Arabs conquered Egypt, they admired Alexandria and its wealth. The Lighthouse continues to be mentioned in their writings and travelers accounts. But the new rulers moved their capital to Cairo since they had no ties to the Mediterranean. When the mirror was brought down mistakenly, they did not restore it back into place. In AD 956, an earthquake shook Alexandria, and caused little damage to the Lighthouse. It was later in 1303 and in 1323 that two stronger earthquakes left a significant impression on the structure. When the famous Arab traveler Ibn Battuta visited Alexandria in 1349, he could not enter the ruinous monument or even climb to its doorway.

The final chapter in the history of the Lighthouse came in AD 1480 when the Egyptian Mamelouk Sultan, Qaitbay, decided to fortify Alexandria's defense. He built a medieval fort on the same spot where the Lighthouse once stood, using the fallen stone and marble.

Description
Of the six vanished Wonders, the Lighthouse of Alexandria was the last to disappear. Therefore we have adequately accurate knowledge of its location and appearance. Ancient accounts such as those by Strabo and Pliny the Elder give us a brief description of the "tower" and the magnificent white marble cover. They tell us how the mysterious mirror could reflect the light tens of kilometers away. Legend says the mirror was also used to detect and burn enemy ships before they could reach the shore.

In 1166, an Arab traveler, Abou-Haggag Al-Andaloussi visited the Lighthouse. He documented a wealth of information and gave an accurate description of the structure which helped modern archeologists reconstruct the monument. It was composed of three stages: The lowest square, 55.9 m (183.4 ft) high with a cylindrical core; the middle octagonal with a side length of 18.30 m (60.0 ft) and a height of 27.45 m (90.1 ft); and the third circular 7.30 m (24.0 ft) high. The total height of the building including the foundation base was about 117 m (384 ft), equivalent to a 40-story modern building. The internal core was used as a shaft to lift the fuel needed for the fire. At the top stage, the mirror reflected sunlight during the day while fire was used during the night. In ancient times, a statue of Poseidon adorned the summit of the building.

Although the Lighthouse of Alexandria did not survive to the present day, it left its influence in various respects. From an architectural standpoint, the monument has been used as a model for many prototypes along the Mediterranean, as far away as Spain. And from a linguistic standpoint, it gave its name -- Pharos -- to all the lighthouses in the world... Just look up the dictionary for the French, Italian, or Spanish word for lighthouse.