London is actually the greenest city in Europe with a total of 13,041 parks . The royal parks are free and open from dawn to dusk. Hyde Park is the largest in central London and is closed to traffic on Sundays. Slap on the sunscreen and play with the squirrels in ST JAMES'S PARK, GREEN PARK, REGENTS PARK, KENSINGTON GARDENS, HOLLAND PARK, KEW GARDENS and HAMPSTEAD HEATH.