Regent's Park, London, UK.
"Known as the 'jewel in the crown', The Regent's Park ... covers 197 hectares. It was John Nash, architect to the crown and friend of the Prince Regent, who developed the Regent's Park as we know it today. A vast rounded park ... surrounded by palatial terraces, a lake, a canal, 56 planned villas (only 8 were ever built) and a second home for the Prince - a summer palace, which was never built. It wasn't until 1835, during the reign of King William IV, that the general public were actually allowed into the sections of the Park. The main development in the 20th century was the creation, in the 1930s, of Queen Mary's Gardens." Source: Park Website