Air pollution and the heat island effect constitute persisting challenges for Athens, which has the lowest per capita green space in the EU and with crisis worsening the availability of resources for urban greening. The dense urbanisation in Athens has been rather recent, rapid, and disorderly. The geomorphology of Athens causes a temperature inversion phenomenon, partly responsible for air pollution problems of two types: high concentrations of particles and photochemical smog. The intense use of automobiles, poor public transportation services, weak cycling network, and lack of green space throughout the city contribute to frequently unsafe air quality levels. This combined with a lack of ventilation in Athens enhances the urban heat island effect, noticed especially during the summer. As part of the 100 Resilient Cities network, Athens has embraced a strategy focusing on being “Open, Green, Proactive, and Vibrant.” Nature-based solutions in Athens are however still scarce and consist mostly of parks, urban gardens, mostly private green roofs, and a few conservation and restoration projects of mostly blue, coastal natural ecosystems.