Retiro Park Between Calles Alcalá, O'Donnell, Menéndez Pelayo, Poeta Esteban Villegas and Alfonso XII. Spread over 118 hectares, the Retiro is the most important park in the city. It was King Felipe IV that ordered the park to be designed at the beginning of the 17th. century. Access to the park was limited until King Carlos III decided to open up the doors to let all of the people of Madrid enjoy it. It is currently one of the "lungs" of Madrid and a place for its people to enjoy as they will. The park is home to a number of attractions, but it is the lake area (where there are rowing boats available) around which passers-by, puppeteers, musicians and people with something to sell tend to congregate. You should also not miss the Palacio de Cristal and Palacio de Velázquez, the Rosaleda and the sculpture of the Fallen Angel, one of the few monuments in the world to the Devil. Royal Botanical Gardens Plaza de Murillo, 2. Another attraction instigated by King Carlos III in 1774. It was finished in 1781 and has a neoclassical design fashioned by Juan de Villanueva. It is home to more than 30,000 plant species and a library that includes a collection of 6,000 slides on the flora of Colombia. The best way to see the park is just to get lost wandering around its paths and thus discover step y step its hidden corners. You should also visit the greenhouses where there is a recreation of different ecosystems including the tropics and the desert. A garden paradise in the heart of Madrid. The Sierra Mountains Madrid also enjoys a magnificent mountain range which in recent years has been benefited by greater environmental protection measures. The Sierra de Madrid covers an area 140 km. long by 25 km. wide. The region of Somosierra is home to sights such as the Somosierra mountain pass, the Montejo reserve and the Peña de la Cabra, in the Sierra de La Puebla. The Guadarrama area is home to the Siete Picos (Seven Peaks) (altitude 2,138 m.), the Navafría mountain pass, the Bola del Mundo (2.258 m.), the Sierra de la Morcuera and the Pedriza, with its strange granite rocks. La Casa de Campo This is the biggest green area in Madrid. Pine trees and thickets are dotted with recreation areas, paths with the routes marked for ramblers, and a lake where there are rowing boats for hire. The Casa de Campo is also the site of the zoo, the teleférico cable car (linking the park and the Paseo de Rosales) and the Parque de Atracciones Leisure Park.