How the Seven Wonders of the Ancient World Work

Scholars have called the Lighthouse of Alexandria the only practical wonder since it served a utilitarian purpose. We have plenty of information about it, but some are conflicting accounts. The story of the lighthouse begins with Alexander the Great.

According to Plutarch, Alexander had a dream in which he was told to seek the small island of Pharos, located just off the coast of ancient Egypt. He chose Ptolemy I Soter, one of his army's generals, to settle the island. Ptolemy decided that Pharos needed something to identify it, both symbolically and literally -- its coast was difficult to navigate.

Some scholars credit the idea for the lighthouse to Ptolemy and others attribute it to the mouseion, a governmental brain trust [source: Smithsonian]. Around 285 B.C., construction began. A man named Sostrates of Knidos was instrumental to the process. By some accounts, he was the financial backer for the project -- the lighthouse cost about 800 talents, bars of silver, equal to roughly three million dollars [source: Princeton]. Other accounts identify him as the lighthouse's architect.

Even if we can't be sure of the lighthouse's architect, we are certain of its architecture. It was built with marble and mortar and composed of three stories. The first level was rectangular, the second octagonal and the third cylindrical. Perched atop the third story was a statue -- either of Zeus or Poseidon, god of the sea. Records from Moorish travelers in the tenth century A.D. say that the lighthouse was 300 cubits high, which converts to about 450 feet (137 meters).

A spiral ramp led to its entrance. Carts and workhorses could be led up to the first level to the hundreds of storage rooms. To access the upper levels, one had to use the spiral staircase. Dumbwaiters lifted supplies to the highest tower.

Ships could supposedly see the lighthouse from a hundred miles away [source: PharosLighthouse.org]. During the day, light was reflected from the sun with a concave metal disc; at night, light came from a bonfire, fueled by firewood or dried animal dung. The lighthouse survived through more than 22 earthquakes before it came toppling down in 1303 [source: Clement]. The people of Pharos loved their lighthouse dearly -- it was a source of power and revenue for the island. They attempted to repair and restore the lighthouse throughout the ninth and thirteenth centuries when it became clear that it could no longer be saved.

Today, a fort stands on its site. The identity of Pharos became so enmeshed with the lighthouse that the lighthouse became alternately known as the Pharos of Alexandria. "Pharos" is also the root of the word "lighthouse" in several languages. And our knowledge of the lighthouse continues to grow after a 1994 archaeological scuba expedition found sunken remnants of the lighthouse.

To learn more about the lighthouse, the other ancient wonders and the new wonders of the world, explore the links on the next pages.