The Pharos of Alexandria was a marble watch tower and Lighthouse built on an island in the harbor of the city. Estimated to have been 300 feet high, the building was erected around 280 B.C. The primary function of the Lighthouse was to guide approaching ships to the harbor on an otherwise unmarked coast. Historians debate whether fires were burned on the top of the tower, or whether mirrors were used to reflect sunlight. Since ships rarely sailed along coasts at night, there may have been little need for light after dark. The Pharos was finally ruined in the 14th Century after having been damaged in several earthquakes.