The Los Angeles River Master Plan was created in 1991 as a plan to restore a large stretch of the river and one of its large tributaries, the Tujunga Wash. Part of the incentive for the project is because the "Great Wall of Los Angeles", one of the largest murals in the world, is painted on the wall of the Tujunga Wash. Other than that, the plan seeks to improve recreation, health, property value, environment, and education in the communities surrounding the river; by building a series of parks. This helps to increase the open space available in Los Angeles; its open space percentage is uncharacteristically low. For example, the city of Boston has 9% open space, over twice as much as Los Angeles' 4% open space.