The Hoyt Arboretum, located within Washington Park and about two miles west of downtown Portland, is home to an outstanding collection of rare and exotic tree species. The 187-acre arboretum is nothing less than a 'living laboratory', and boasts more than 10,000 individual trees and shrubs, from more than 1,100 different species - including a few specimens of Dawn Redwood, a tree which was thought for many years to be extinct. The trees are arranged by taxonomy and geography, and are labelled so that visitors can learn more about the ones they find particularly memorable. The arboretum consists of 12 miles (19km) of walking trails, a visitor's centre that is open six days a week, an enormous picnic shelter, and a meadow. Guided tours are available Saturdays between June and September, for a small fee. Visitors of all ages will enjoy spending time in this 'urban oasis' on the banks of the Willamette River.