An abundance of wildlife (more than 112 bird and 62 mammal species) can be found in Forest Park. With its massive tree canopy and substantial undergrowth, the park serves as a natural air purifier, water collector, and erosion controller. The 30-mile Wildwood Trail in Forest Park is part of the region's 40-Mile Loop system that links Forest Park to pedestrian and trail routes along the Columbia River to Gresham, through southeast Portland, along the Willamette Greenway, and back to the Marquam Trail in southwest Portland. A landmark on the trail is the Stone House. This structure was built in the mid-1930s by the Works Progress Administration (WPA) as a public restroom. The infamous Columbus Day storm on October 12, 1962, took out the water line. Because the structure had been heavily vandalized over the years, the decision was made to gut the building rather than embark on costly repairs. It remains as a favorite spot to rest along the trail.