According to Donella H. Meadows' 1972 book entitled "The Limit to Growth" the global environmental carrying capacity that until now had been almost thought limitless has gained prominence again as well. Human production and consumption will rely on our natural resources and ecosystems. A rapidly growing world population places ever-greater demands on these resources in general. Looking ahead 100 years or more into the future, the key point in urban construction projects is undoubtedly "sustainable." Under present circumstances where the sea level continues to rise and global climate changes have brought about very real fear of large-scale flooding in many local areas, safety in most urban areas around the world cannot be guaranteed without massive public spending. To make matters worse, if these large-scale flood prevention measures were destroyed, the resulting catastrophe will claim many lives in an instant. Actually, in March 11, 2011, powerful breakwaters constructed near had been completely destroyed by tsunami, resulting in tremendous numbers of victims. The shocking truth highlighted by this disaster was that it is impossible to counter such extreme power of nature by using huge civil engineering structure.

We thus decided that, for water-related disasters as exemplified by floods, the answer lies not in dealing head-on with these problems using massive structures like dams and/or dikes and seawalls but taking the indirect approach of simply taming the water, to keep to a minimum the effect of water-related disasters in a more economical manner. As the final countermeasure, therefore, floating structure is considered to be excellent against the water-related disasters. A number of proposals to build floating structures began to emerge from the late 1950s as a means to address land and population issues and various proposals of floating city for civil purpose were suggested by worldwide architects. In the 1980s, many offshore structures including floating platforms have been built for the purpose of drilling offshore oil and oil production. During this era, the technology for floating structures was established and advanced drastically in such fields as ocean engineering or naval architecture.

On the other hand, in the history of urban area, urban sprawl due to automobile life has become a big issue because of an inefficient consumption of energy and costly urban infrastructures. Then many specialists such as architects, city planners and so on highlight the relationship between urban form and sustainability, the suggestion being that the shape and density of cities can have implications for their future. From this debate, the idea of a compact city was born as the most sustainable urban form. A compact city has many excellent characteristics such as the central area revitalization, high-density development, mixed-use development and diversity of various services and facilities. There are many perceived benefits and merits of the compact city over urban sprawl appearing all over the world recently. They include lowered dependency cars meaning lowered emissions, reduced energy consumption, reduced pollution, increased overall accessibility and so on. However, the key bottleneck of the compact city is that no genius architect and/or city planner can design. Producing the perfect form which provide for future city functions and size properly from the present knowledge of city planning in case of city on land is impossible. Then the best way to solve this problem is how to transform city in a short time in order to fit future needs for city. We believe the best solution lies on the combination of the compact city concept and the floating structure.