Madrid is the European city with the highest number of trees and green surface per inhabitant and it has the second highest number of aligned trees in the world, with 248,000 units, only exceeded by Tokyo. Madrid's citizens have access to a green area within a 15 minute walk. Since 1997, green areas have increased by 16%. At present, 8.2% of Madrid's grounds are green areas, meaning that there are 16 m2 of green area per inhabitant, far exceeding the 10 m2 per inhabitant recommended by the World Health Organization. Buen Retiro Park, formerly the grounds of the palace built for Felipe IV, is Madrid's most popular park and the largest park in central Madrid. Its area is more than 1.4 km² and it is located very close to the Puerta de Alcalá and not far from the Prado Museum. A magnificent park, filled with beautiful sculpture and monuments, galleries, a peaceful lake and host to a variety of events, it is one of Madrid's premier attractions. The park is entirely surrounded by the present-day city.