A Paris garden in the sky

Green walkways: a brilliant way to link and rejuvenate inner-city areas. In 2009, New York opened the High Line park, using a 1.5-mile stretch of abandoned elevated railway, while Chicago has plans for a nearly three mile-long Bloomingdale Trail, again along a disused rail line. In London, two architecture firms have won a competition to design a landscaped walkway just south of the River Thames, joining galleries, public works of art and an open-air auditorium.There’s also a proposal by Thomas Heatherwick, the designer behind the stunning Olympic cauldron, for a floating garden to bridge the Thames from Covent Garden to the South Bank.

But the project that started it all is in Paris - the Promenade Plantée, an aerial nature walk opened late last century (above and left). It snakes through the 12e arrondissment, using a derelict 19th c railway viaduct that once took passengers from Bastille, in the city centre, out to the leafy Bois de Vincennes. When the line was closed in 1969, the structure became a decaying eyesore. But instead of pulling it down, the authorities transformed it into a garden. The arches below became the Viaduc des Arts, with shops showcasing crafts such as cabinet making, tapestry restoration and interior design.

It’s easy to find. Walk south-east from Opéra Bastille along Rue de Lyon, into Avenue Daumesnil and you’ll see the walkway arches, surrounded by apartment buildings and offices. It runs for more than two and a half miles, later descending to street level and into tunnels. At times the path widens to formal parterres with trellised arbours, at others it becomes a narrow corridor, edged with trees. It’s a favourite with joggers, office workers on their lunch breaks, and parents with energetic youngsters. (At one point it overlooks a playground.) Local residents use it as a meeting place while garden enthusiasts linger over the planting. I saw one father using it to teach his young son about the way things grow. For tourists, it's a welcome contrast to the more usual sights. Even if you walk just a small section, you’ll never forget it. Take a picnic and prepare to be inspired.