This chapter explores the international legal framework required to support floating cities as adaptive solutions to rising sea levels and as alternatives to the displacement of coastal populations. While climate change poses significant risks to low-lying coastal areas, Small Island Developing States (SIDS) face an additional existential threat as sea level rises challenges established principles of statehood, sovereignty and maritime rights under international law. Floating cities, as innovative urban environments, offer a potential pathway for preserving statehood and addressing global environmental challenges. However, the classification of floating structures under frameworks such as the United Nations Convention on the Law of the Sea (UNCLOS) remains ambiguous, complicating their governance and integration into international law. This chapter argues that recognising floating cities as sovereign extensions of submerged territories should be considered an erga omnes obligation, reflecting the collective responsibility of states to address climate-induced displacement and uphold fundamental human rights. By examining structural characteristics, jurisdictional complexities and emerging legal norms, this chapter highlights the need for international cooperation to develop a unified framework for floating cities. Such recognition would ensure the preservation of maritime zones, support the rights of vulnerable populations and foster global resilience to environmental change.