The design research is based on the scenario that the sea level will rise 10m in 2121. If that happens, what can Ma Wan Island, a small island in Hongkong, be like at that time? How can I design a city based on that? My proposal takes environmental change, the connection of different areas, and the coexistence of various species into account, trying to make habitats for all creatures. The island will return to nature, and a new city will be built around the island as the home for citizens and an essential pier connecting Hongkong and China's mainland. The design also considers the alternative function of the same structure in different phases. For example, the bank can reduce the impact of the sea-level-rising and high tides at the beginning, buying time for the city construction; in the second phase, its function will convert into artificial reefs, helping recover the ocean ecosystem.