City Diplomacy refers to the participation of subnational actors—cities, regions, and networks—in international affairs. Yet in the 21st century, this practice extends far beyond local boundaries. Today, it stands at the intersection of multilateral governance, climate diplomacy, digital transformation, and global security, reflecting the complex interconnections shaping the international system.

The first axis focuses on sustainable and resilient development. Local and regional governments play a vital role in implementing global frameworks such as the UN 2030 Agenda and the Paris Agreement. Their initiatives on climate adaptation, green transition, and social inclusion translate global commitments into tangible local action.

The second axis highlights digital transformation—the technological revolution reshaping governance, economies, and diplomacy itself. As cities adopt smart governance, AI, and data-driven policymaking, they not only modernize public services but also help define global debates on ethics, privacy, and power in the digital age. In this sense, digitalization becomes a new arena of diplomacy, influencing cooperation, competitiveness, and trust among nations and local actors alike.

The third axis, international engagement, concerns how cities and territories project themselves globally—through cooperation frameworks, partnerships, and participation in multilateral networks. This engagement goes beyond city branding; it contributes to shaping norms, advancing shared agendas, and building collective responses to global challenges.

These processes unfold within a multi-layered system of diplomacy:

• A macro layer of global institutions and geopolitical blocs;
• A meso layer of regional cooperation and inter-state relations; and
• A micro layer where cities, private actors, and civil society engage directly in international dialogue.

Understanding these layers together is crucial to navigating today’s geopolitical landscape—one defined by climate instability, digital competition, and new security paradigms.