Finally, let's take a look at five of the most interesting lighthouses in history:
The Pharos of Alexandria
First constructed around 270 B.C., in ancient Egypt and one of the Seven Wonders of the Ancient World, the Pharos of Alexandria is widely believed to be the first lighthouse in existence. It also might have been the tallest structure on the planet: Estimates claim the three-tiered lighthouses might have reached up to 450 feet (137.16 meters) tall. The beacon was a fire burning in an open cupola -- a small glass device -- that was reflected onto the water with a mirror, guiding ships into the port of Alexandria. An earthquake destroyed the structure in 1326 but undersea remnants of the lighthouse were discovered in 1994.
The environment around Eddystone Light in Plymouth, England was so inhospitable that this lighthouse had to be built four times. Henry Winstanley started construction on the first wooden structure in 1696 and, after he was captured and briefly imprisoned by the French, the lighthouse was lit in 1698. In 1703, the already damaged lighthouse was swept out to sea. The next iteration lasted from 1708 until it burned down in 1755. Next, esteemed engineer John Smeaton built a lighthouse with a broader base that lasted for 123 years, until a concerned Trinity House disassembled the lighthouse for fear that it would be destroyed in 1882. The same year, James Douglass used larger stones and a more precise design to build the lighthouse that stands today, 14 miles (22.5 kilometers) off the coast.
Established at the entrance to Boston Harbor on Little Brewster Island, Boston Light is a bookend of sorts for American light keepers. It was home to the first paid keeper, George Worthylake, who was assigned in 1716, and it also remains the only manned lighthouse in the country. Each year, the 8-mile (12.87 kilometer) Boston Light Swim, the oldest open-water swim marathon in the country, is held in the surrounding waters [source: Boston Light Swim].
Cape Hatteras Lighthouse
Measuring 208 (63.39 meters) feet tall, Cape Hatteras Lighthouse in North Carolina is the tallest lighthouse in the nation. It lords over the Outer Banks, a particularly precarious stretch of the Atlantic Ocean that has earned the moniker "Graveyard of the Atlantic" for the untold number of shipwrecks that have occurred there.
St. George Reef Lighthouse
Built between 1882 and 1892 on rocks a few miles off the coast of Crescent City, Calif., St. George Reef Lighthouse is believed to be the most expensive lighthouse ever built in the United States. The price tag? More than $700,000 [source: St. George Reef Lighthouse Preservation Society].