Rome owns a unique territorial heritage that is still remarkably free from urban development. After the adoption of the "Piano delle Certezze" in May 1997, the 64% of the town territory (80,000 of the 129,000 total hectares) is now subject to very strict regulations for the protection of the environment. RomaNatura has been entrusted 14,000 hectares, which is more or less the area covered by the entire city of Bologna. The Royal Parks Constabulary of London manages little more than 2,500 hectares of land. Archaeological finds, historical monuments, villas and castles are only a part of the treasures offered by this great heritage: the real treasure is made of a number of ecological "islands" providing a natural habitat for over 1,000 different species of plants, 5,000 species of insects, and 150 species among mammals, birds, amphibians, and reptiles. Many of these areas are still used for farming, and the Municipality of Rome is still the largest agricultural town in Italy.