The continuous drive toward progress necessitates new models and spaces for urban development, a challenge further complicated by the awareness of the impacts caused by human activities and of the growing population needs. In this context, the floating city represents an innovative solution aiming to revolutionize the traditional concept of living, while simultaneously addressing the issue of rising sea levels due to global warming. Currently, research on floating cities is still in its early stages, with the Oceanix Floating City in Korea, the Maldives Floating City, and the Floating City proposal at the 2023 Venice Architecture Biennale among the world’s first projects in this regard. The aim of the research presented in this work is to develop an innovative concept of a modular floating city, designed considering urban and livability standards different from the traditional ones, and utilizing cutting-edge materials and technologies. The proposed concept is highly scalable, to accommodate a variable number of inhabitants, and environmentally friendly, as it auto-produces locally the required energy from renewable sources. The innovations it introduces are not limited to the floating context and to the technical aspects but concern the vision of space, which becomes more resilient to better address the needs of the inhabitants and their well-being. The chapter presents the conceptual description of the floating city, focusing on how the new concept of “urbs” was generated, the chosen forms, materials, and technologies, the presence of greenery and suitable services, and the floating and protection systems necessary for its stability/life at sea. Finally, by considering a specific case study of 50,000 inhabitants, it outlines a preliminary quantitative analysis aimed at evaluating the general dimensions and the energy sustainability of the floating city.