Brutal, neglectful and vain, Nero currently enjoys a reputation as one of the worst of the Roman emperors, but in one respect at least he deserves acknowledgement as a pioneer in the development of the modern cities more and more of us inhabit. Rome was devastated by fire in 76AD — a fire Nero was said to have done nothing to fight (and may even have started) and which he blamed on Christians, many of whom he executed without trial. On the site of this fire Nero created an innovation in city planning which was unprecedented then and which has since become integral to the health and sustainability of today’s conurbations: the city park. Nero’s park was large scale and free for all to enjoy, featuring both open spaces for relaxation and carefully groomed planted areas (as well as numerous statues of himself). Thus he created the template for our modern city spaces.

In our more recent past, crowded and squalid cities have needed green areas for the populace to enjoy, and such needs were met by philanthropic donations of land or the absorbing of private lands, once the preserve of the powerful few, into public ownership. Today’s city parks and public spaces are valuable and cherished because they offer something for everyone: they are instruments of social cohesion. There is room for a myriad of activities: sporting, from the solo jogger cocooned by his earphones from social contact, to gregarious footballers; artistic, from people writing, reading or painting in some secluded spot to participating in open-air exhibitions and concerts. For the romantically inclined, parks are natural locations for assignations, whilst children revel in the opportunity to run and play in the open air, away — momentarily at least — from less vigorous counter-attractions at home, like the television and the internet.

There are other, more psychological reasons why such open spaces, amidst the density of our cities, improve our well-being. It can sometimes seem that life in modern cities engenders an impatience, a focus on the instant, the latest, the superficial. Parks are none of these things. Our green spaces give us a sense of not being in a city at all, but of our having stepped aside, temporarily at least, from noise and pressure into an environment where we can pause, reflect and recharge. As our cities grow ever outwards and upwards, and the glass and steel of the urban skyline seem ever-changing, our parks and green spaces are pleasingly unaltered, except for subtle changes as the seasons creep round. In these sanctuaries of calm we can do nothing at all, guiltlessly; or pursue activities that are impromptu, purposeless and ungainful — so different from the values of the world outside the parks’ boundaries. The contact we have inside park gates with the natural world — albeit a world carefully maintained, even manicured — is soothing to the stressed soul.

Today, further evidence of their value to us is provided by the ecological perspective. There is a growing awareness and appreciation of the ways in which these spaces are not just passive areas for tranquillity and socialising but also provide a vital counterbalance to the perceived debilitating impact cities have on the environment. Cities are heat islands: their buildings, vehicles and concrete generate or reflect heat. Vegetation, on the other hand, cools: partly by providing shade, but mostly through water evaporation from leaves, like perspiration from our skin. But it does not stop there. Trees and plants are like lungs, filtering the air and water of pollutants. They increase the capture of rainwater, improving drainage. They reduce noise pollution by the dense screening they can offer. They provide habitats for a diversity of species of wildlife.

It is little wonder then that there are projects around the world to reclaim waterfronts and derelict land, however unpromising for renewal some may seem. In New York, for example, an abandoned elevated railway, overgrown with self-seeding grasses and trees during twenty years of inactivity, faced demolition. Then a local group campaigned successfully for its regeneration as a landscaped public greenway above the streets of its former meat-packing neighbourhood. Today, the many pedestrians drawn to the High Line seem undeterred by the restrictions on its use: no joggers, skateboarders or cyclists; no music, alcohol or pets. In return, they enjoy fresh vistas and perspectives of their city as they walk the paths between the vegetation and the occasional piece of exposed track, a deliberate reminder of the space’s former life. As a direct consequence, shops and cafes have sprung up in the vicinity, and the local economy is undergoing a renaissance. Ecological and economic benefits go hand in hand.

On a smaller, more local scale, city residents around the world are greening their roof spaces and their balconies, planting in their courtyards, and creating community gardens. These play an important role in enhancing feelings of kinship and belonging by drawing people out of their houses to congregate and socialise. Once a feeling of ownership of the space is established, members of the community are more proud of it and more vigilant, which leads to greater safety.