Artificial island
An artificial island is an island that has been formed by human, rather than natural means. It is usually constructed on an existing reef or may be an expansion of a small natural islet. Traditional artificial islands are created by land reclamation, although some recent developments have been constructed more in the manner of oil platforms. Another, less distinctive, type of artificial island is formed by the incidental isolation of an existing piece of mainland by canal construction.
Despite a popular image of modernity, artificial islands actually have a long history in many parts of the world, dating back to the crannogs of prehistoric Scotland and Ireland, the ceremonial centers of Nan Madol in Micronesia and the still extant floating islands of Lake Titicaca. The city of Tenochtitlan, the Aztec predecessor of Mexico City, was home to two hundred fifty thousand living on a large artificial island in Lake Texcoco.
Many artificial islands have been built in urban harbors to provide either a site deliberately isolated from the city or just spare real estate otherwise unobtainable in a crowded metropolis. An example of the first case is Dejima (or Deshima), built in the bay of Nagasaki in Japan's Edo period as a contained center for European merchants. During the isolationist era, Dutch people were generally banned from Nagasaki, and Japanese from Dejima. Similarly, Ellis Island, in Upper New York Bay beside New York City, a former tiny islet greatly expanded by land reclamation, served as an isolated immigration center for the United States in the late 19th and early 20th century, preventing an escape to the city of those refused entry for disease or other perceived flaw, who might otherwise be tempted toward illegal immigration.
See also: List of artificial islands