Cities have an undoubted significant role in climate change mitigation. Several cities across the globe have made commitments to sustainability transitions through green strategies. In the recent past, Europe has witnessed a surge in the development of smart cities and advancement towards creating more sustainable cities. At the moment, the concept of Positive Energy Districts (PEDs) further encourages districts and cities to change their business-as-usual ways to be more carbon neutral. This paper looks at the five cities of Maia, Reykjavik, Kifissia, Kladno, and Lviv that are a part of an ongoing Horizon 2020 project. The purpose of the paper was to understand the steps the cities have taken to select the 10 solutions for replication. The information was collected through discussions, interviews and implementation plans developed by each city. It must be highlighted that each city’s circumstances differ in terms of political support, finances, technical expertise, and stakeholders’ interest, and this applies to all world cities when discussing the implementation of new efficient solutions. Cities across Europe and beyond may find themselves in a similar situation, and therefore, this paper also provides a story of the five Fellow Cities as they transition towards PEDs.