There is something eerie about Central Park at night, the suggestion of a ghostly mist lingering about its less well-lit corners. And there are many of those. It’s probably just car exhaust fumes, but eerie all the same. Pick up any tourist guide to New York and even the most basic of facts relating to one of its most famous attractions are impressive: over 843 acres (340ha) of man-made parkland augmented by lake, loch (in name anyway) a reservoir, a zoo, a dairy, a sheep meadow and a castle, to list but a few of its features. The park is also a thriving ecosystem, the city’s living lungs, threaded through by skilfully designed sunken roads and pathways; no two of the bridges that straddle them are alike.