With nearly 70% of the world population expected to live in cities by 2050, assessing the sustainability of urban systems, both existing and future ones, is becoming increasingly relevant. Making cities more sustainable is a global priority, which is highlighted by ‘Sustainable Cities and Communities’ being listed as one of the Sustainable Development Goals (SDG) adopted by United Nations Member States in 2015. This Virtual Special Issue (VSI) explores the implementation and assessment of policies and technologies that contribute to the transition to a sustainable, energy efficient and regenerative society. We organized the issue according to four main research themes: 1) Renewable Energy Systems (i.e., different types of systems, qualitative assessments and public acceptance); 2) Sustainable Built Environment (which includes construction, operation and refurbishment); 3) Multi-Scale Models (considering urban sustainability transition from building to districts, or cities and regions to multi-country comparisons and their scaling across different countries); and 4) Governance and Policy (climate change mitigation and adaptation plans/policies that are reported across countries, urban services and infrastructures). This paper serves two purposes. The first is to provide an analysis about patterns, correlations and synergies found across the different topics that have been addressed over the last 20 years in the literature about cities’ sustainability paths. A bibliometric analysis and a contingency matrix show the degree of correlation between scientific journals and main topics addressed by published articles. Secondly, the paper acts as an Editorial to the VSI, introducing the wealth of research articles and topics included in it. Both the bibliometric analysis and the papers published in this VSI demonstrate the interconnectedness of energy consumption, pollutant emissions and the competition for finite resources. The aim is to present advances and challenges of this exciting and ever-evolving research field to inform and guide future studies of urban sustainability.