This chapter, addresses the planning, design, and project management aspects of megaprojects (locally executed institutional arrangements and financing at various spatial scales) as well as the larger causal context (trajectories and transitions) of neoliberalism, globalization and competitiveness, megaregionalization, strategic connectivity, and increased geopolitical competition, which explain the rise and development of megaprojects and its linkages with socioeconomic development worldwide. The title of the chapter also refers to the trajectories and transitions in urban political economies toward the coexistence of the focus on property development, culture, and iconic architecture over the past 30 years with a new interest in science and technology, innovation, and sustainability as strategies to foster global competitiveness (Chaps. 3 , 4 , 5 and 6 ). This chapter analyzes megaprojects in a dual, interconnected way: as spatial settings and infrastructure units that obey specific planning, design, and management priorities, as well as reflections or expressions—as consequences or crystallization—of larger socioeconomic forces. This chapter introduces the reader to the analytical themes that frame Chaps. 3 , 4 , 5 , 6 , 7 and 8 : complexly disruptive impacts and sustainability.