**Preface to "Smart Cities and Positive Energy Districts: Urban Perspectives in 2021"**

Cities and urban areas are the nexus for the transformations required if the EU is to achieve the targets of the European Green Deal, to fulfil commitments related to the UN's Agenda 2030 Sustainable Development Goals (SDGs), UN-Habitat's New Urban Agenda, the Urban Agenda for the EU, the Paris Agreement and provide support for the New European Bauhaus movement as well as EC Mission 100 Climate and Neutral Cities.

The urban nexus challenge is primarily characterized by the need for integrated approaches and to translate research and innovation results to actions as urban governance is still too fragmented and siloed; therefore, support for cities across levels of government is often insufficiently coordinated as public authorities often lack knowledge.

Since its creation in 2010, the EERA Joint Program on Smart Cities has accumulated important knowledge on specific topics of the program.

This includes Smart Cities and Positive Energy Districts, not only a crucial topic tackled by the EERA Joint Program on Smart Cities Workplan but also by Horizon Europe, and/or on a national level, focusing on innovative solutions based on interdisciplinary approaches, which are needed to face the highly complex structure of the transition towards sustainable urban areas.

Thanks to the most prominent national and international RD&I programs, many case studies, best practice and success cases have been completed, are ongoing, or are in their planning stage.

Accordingly, this Special Issue is promoted to support the publication of the most promising research and innovation projects established by EERA JPSC partners in recent year so as to spotlight EERA JPSC, which is not only a platform for prominent voices in the research area in Europe capable of highlighting different points of view and a variety of solutions, but also highlights selected effective interventions to support cities in their efforts to become climate neutral.

The Special Issues Series Coordinator, Paola Clerici Maestosi, conceived the Series in 2018, at a time where the need for knowledge about Smart City projects was high, thus supporting the idea to collaborate across countries thanks to the EERA JPSC network. Between 2018 and 2021, more than 70 papers from more than 10 European countries were published.

> **Paola Clerici Maestosi** *Editor*
