Manhattan still loves the high life

New York's beloved sky park, the High Line, is about to double in size. The former railway has helped change the way a whole area sees itself.

The stereotypical New Yorker: assertive, fast, sceptical, focused on making money and determined to turn every moment into an achievement. This month, a linear sanctuary elevated above Manhattan is being doubled in length, challenging our ideas of these ultimate urban dwellers with lessons for those of us who live in cities everywhere.

This June, the celebrated High Line, the park which runs along the West Side of Manhattan, will flow from the heart of the stylish Meatpacking district through fashionable Chelsea all the way up to 30th Street. Though the extension of this former raised railway has not yet been opened, you can glimpse its promise through still-locked gates.

Section Two will include as much of a forest as you can cram into a narrow railway, "The Chelsea Thicket" of winterberry, redbud and large American hollies – and something rare and precious in Manhattan: an expanse of lawn. The Lawn "peels up" at 23rd Street to offer a vantage point of both sides of Manhattan Island.

Since the original High Line opened two years ago, people have come to use this raised urban park in a unique and subtle way, almost as if they were wandering around an art gallery. You can't run with your dog, skate or cycle through the High Line on your way to somewhere else. Instead, the meandering stream of wooden paths, which you are forced to take to avoid stepping on the "wild" species, encourages you to take your time. The height of the park provides a new perspective on the skyscrapers, water towers and fire escapes around you.

Instead of getting you to where you need to be quickly, the High Line celebrates attention to the very moment, echoing the thriving mindfulness movement led by Jon-Kabat Zinn. His meditation classes, books and CDs have become increasingly popular as a way to become aware of what he calls the nowscape.

I saw visitors taking off their shoes and wiggling their toes as they dipped them into a stream of water, looking intently at a plant with red, comically wavy arms, or pointing out small architectural details of the surrounding warehouses. The idea of street as theatre, and the park visitors as an audience of the New York street, is formalised in the tiered wooden seating which invites you to sit down and view 10th Avenue through a large transparent sheet. When Section Two opens you'll have the opportunity to compare life here with the viewing spur at 26th Street, where you can look at a different section of 10th Avenue through a re-imagined billboard.

This precious opportunity to step out of time has been carefully protected against an excess of commercial encroachment. While there is space to eat, on carefully scattered tables and chairs, there are no food or drink stalls. When Section Two opens, this purity will be challenged, but only by those who offer food that is "thoughtful and creative". Artists are permitted to talk about and sell their photographs, paintings and jewellery, as long as they have created their work themselves. Public art blossoms, like the current bell-sound installation by Stephen Vitello. Every minute his "bell tower" tolls with an everyday sound recorded from somewhere in the city, ranging from a child's toy phone to a boxing-ring bell. This presents you with a way to tune into sounds we often ignore.

I came to know a less-salubrious side of this area in the course of my first job in New York many years ago. I was sent to the area around the Meatpacking district to convince young male and female prostitutes to leave their haunts around the vacant parking lots and venture up-town to Columbus Circle and the studios of public TV to join in a discussion on street children. I only later came to understand the dark fear that this part of town engendered in many New Yorkers.

Today the area has been transformed. There are still cobbled streets and occasional signs for Milano's Italian Sausage and Weichsel Wholesale Beef & Lamb, but these are nestled between high-end boutiques from Alexander McQueen and Dolce & Gabbana. The hip Standard Hotel bestrides the High Line, with its roof-top night club equipped with a plunge pool. Yet Standard visitors aren't able to slip into this sanctuary directly from their five-star luxury. Like everyone else, they must ascend the metal staircase one block down.

The democratic nature of the High Line is also reflected in the way the park is funded. It is owned by the city itself, while the non-profit Friends of the High Line, employs the gardeners. There are frequent notices to encourage you to become a friend but, rather than money giving you access to an exclusive society, these are public clubs which confer their privileges, plants or programmes, upon every member of the community. Some stretches of the park are sponsored, by Tiffany's or a generous individual, but this is only recorded in discrete metal plaques.

The High Line also offers us a new way of engaging with nature in the city. With a touch of irony, it introduces an element of wildness which echoes its abandoned origins. When the freight trains stopped shunting milk and meat along the tracks in 1980, the disused line provided shelter for wayward seedlings which planted themselves in the decaying metallic structure. The landscape architects who created the park drew inspiration from what had grown wild and today the park shows off no exotic varieties of plants, largely nurturing those which are native to the North-east US. Section Two will feature a wildflower field full of perennial blooms, which naturally alter every few weeks. Despite the rich array of tulips and cat's tail grasses which are lovingly chosen and carefully tended, they sprout amid the railway tracks as if they were self planted. From street level, you can see hints of hidden green spilling over the metallic sides. Casper, a German High Line park gardener, told me that when the Sumac tree is open fully in summer, he revels in seeing its palm-tree profile visible from street level.

Perhaps more than any other city, Manhattan has self-consciously unfolded on multiple levels. The shortage of space due to the limits imposed by the surrounding water has encouraged New Yorkers to gaze skywards and nurture their roof gardens. The High Line draws upon the ideas of the French architect Le Corbusier who tried to create garden cities in the air.

But all cities, especially those with deep historical roots, are also multi-levelled, with past generations hiding their secrets beneath our feet.

I feel renewed cycling alongside the canals of London, which flow like deep cuts through that city. I can fly free of traffic lights and 21st-century congestion and touch London's early industrial past. The High Line, in contrast, lies above the present-day ground level, hinting towards the future, with birch and magnolia trees challenging our very idea of what is ground. Perhaps because of the evolutionary advantage that a greater height gave us on the wild savannah, looking down on the world increases our sense of wellbeing and encourages us to think beyond our quotidian concerns.

Though the High Line is only two-years old, it is already cherished by New Yorkers and tourists alike. Its value doesn't come from a deep historical tradition, but rather because it has been salvaged from destruction, as a record of renewal and restoration. While it is apart from the city, it is not remote; you literally vibrate with the buzz of the world below. There is no silence but a celebration of all that New York offers, but one step removed. You are encouraged to contemplate the city's past and your place within the New York narrative without being seduced by its glittering charms. In a city where you traditionally have had to spend money to have a real experience, the High Line is teaching New Yorkers how to reflect and enjoy being a little more austere without feeling deprived.

Emily Kasriel is executive producer of 'The Forum', the BBC World Service programme about ideas

The parks that gave green life to urban decay

Turia Gardens – Valencia

When the Turia River flooded Valencia in 1957 and caused extensive damage, residents decided to divert it and turn its bed into parkland. This park snakes through the centre of the city, injecting a green vein between the old and new parts of the Spanish port city.

Parkland Walk – London

This former railway runs from Finsbury Park to Alexandra Park and is London's longest local nature reserve. It follows the path of the disused London and North Eastern Railway and abandoned stations can be spotted among the wildlife.

Jackson Square – New Orleans

Situated in the French Quarter, Jackson Square was originally called the Place d'Armes and was a place for military parades and public hangings. Declared a National Historical Landmark in 1960, it is now one of the most lively and well-used parks in New Orleans.

Promenade Plantée – Paris

The Promenade Plantée and Viaduct des Arts follow the old Vincennes railway line. With the reformed viaduct's arches containing shops, restaurants and showrooms, the idea was to bring culture and life to a struggling area of Paris. The park, running for three miles from the Bastille, features landscaped gardening and an elevated walkway similar to the High Line.