Built: About 304 B.C.

Location: On ancient island of Pharos in harbor of Alexandria, Egypt

History: Upon its completion, the Alexandria lighthouse -- commonly estimated to have been about 400 feet high -- was one of the tallest structures on Earth. The Greek architect Sostratus designed it during the reign of King Ptolemy II. The Pharos guided sailors into the city harbor for 1,500 years and was the last of the six lost wonders to disappear. Earthquakes toppled it in the 14th century A.D. An Arab traveler made notes in 1166 that provide intricate details on the structure. From his writing, archaeologists have deduced that the lighthouse was constructed in three stages. At the top, a mirror reflected sunlight during the day, and a fire guided sailors at night. The structure was so famous that the word "pharos" came to mean lighthouse in French, Italian and Spanish