The Lighthouse of Alexandria, one of the Seven Wonders of the Ancient World, is undoubtedly one of the greatest architectural feats of antiquity. The Lighthouse of Alexandria was at least as tall as a 25 story modern building and stood for over 16 Centuries - from the mid-3rd century B.C. to the 14th century A.D. when an earthquake shook its remaining segments down. Some of its structure survives as stone building blocks for a small on-site castle fortress - some others lie submerged in the lapping Mediterranean Sea. The Pharros of Alexandria (as the structure is also known) served a useful function - its burning flame could be seen at night by faraway ships seeking the harbor's shelter.