Artificial islands were islands created by man. They increased real estate.
Humans originated in Africa 200,000 years ago. 50,000 years ago, humans reached Australia and modern-day Indonesia. As thousands of years passed, humans colonized every continent on Earth except Antarctica. They also colonized islands. The Austronesian peoples originated in Taiwan, then known as Hawaiki. They spread out all over the Pacific Ocean, colonizing many islands including Hawaii. They also colonized as far west as Madagascar. There last colony was New Zealand in the 1300s. They also once ruled Southeast Asia and, in Thailand and Laos, still did. In the late 2nd millennium, the Austronesian peoples became pretty much part of the Western world. Island colonization continued into the 21st century, only this time with artificial islands.
There were two kinds of artificial islands: offshore artificial islands and deep ocean artificial islands.
Offshore Artificial Islands
Tech Level: 10
Artificial islands were nothing new. Tenochtitlan was possibly an early artificial island. More modern artificial islands followed the example of Tenochtitlan. Only this time, they went into the ocean. The first offshore artificial island was Kansai International Airport in Osaka, Japan in 1994. Hong Kong International Airport was a larger artificial island built out of two natural islands. In the early 21st century, Dubai became home to several artificial islands. Pylons were used to keep erosion from occurring. Artificial islands also added more shoreline to Dubai and other coastal cities. Configuration was dependent on purpose. These artificial islands could be built at a depth of 15 meters or less. New techniques for even greater depths.
Deep Ocean Artificial Islands
Tech Level: 11
Techniques for building artificial islands in the deep ocean were available in the mid-21st century. Large pylons of concrete and steel were used to anchor the artificial islands at 30 feet or deeper. The surface platform was also modular and had multiple levels. The islands were large and used techniques to remain stable most of the time. Some artificial islands floated in the sea. They had many applications. One of them was as energy islands.