The key challenges facing our cities Cities in Europe have undergone many changes during the Covid-19 pandemic. New cycle lanes have appeared where traffic jams used to clog cities' arteries and pollute the air. New plants and trees have been planted where thousands of pedestrians used to endlessly stroll. These small changes are a positive, yet simultaneously reserved response to today’s health and environmental challenges: what we need is a structured response to ensure both human and environmental well-being in the longer term.