Forest Park, Portland
I'm not sure where the main entrance to Forest Park is -- I have a friend who lives next to it and my entrance is her backyard. Anyway, this is the largest urban wilderness park in America, and despite the annoying horns and whistles that come from the train tracks along the river it still makes good hiking and exploring.
This tip is divided into several different categories, due to the number of items operating at the Audubon Society of Portland facility.
The "Pittock Bird Sanctuary" of the facility consists of 143 acres of forest land owned by the Audubon Society of Portland and maintained in a state that encourages birds to visit. There are a number of hiking trails in this area, and heading east from the society's office on a trail will also lead you to Upper MacLeay Park and the Wildwood Trail, and the network of forest and trails that are associated with Forest Park and Washington Park.
The "Pittock Bird Sanctuary" has a number of places in it designed specifically for people to sit and wait for birds to show up, and thus there are a number of benches, plus an artificial pond and overlook shelter to encourage water birds and some amphibians to live here.
The web site features a PDF map of the trail system in the sanctuary.
Audubon Society of Portland also has a wildlife store and a wildlife recovery center, as well as operating a number of programs at its offices here.
While it is a popular destination for those who know about area wildlife, or those who don't know much about area wildlife and are interested in learning, this is a popular place to come. However, few people from outside the Portland area know of this little facility.
If your in Portland Or and you don't ride a bike, you are certainly missing out. Portland is one of the major bike capitals of country. There are bike lanes everywhere, and if you are a more serious rider you can explore Forest Park (one of the biggest urban parks anywhere.) if you are even more serious, take your skinny tire'd bike for a few laps up on Skyline Dr. On your way back into town be sure to stop in any of the amazing coffee houses for some of the best brews.
As mentioned previously, Forest Park is the largest forested city park in the US....and it is amazingly easy to get to from downtown.
The easiest entrance (and I think one of the simplest trails) is Lower Macleay. The entrance is at 29th and Vaughn in NW Portland (you can take the #15 bus right from downtown and ask the bus driver to drop you off there). Take the stairs going down from the overpass and you are there.... Lower Macleay has a branch off onto the Wildwood Trail, otherwise you can go up through upper Macleay and when it meets the road cross it and access more trails. In it's entirety Forest park has over 70 miles of trails! :)
Forest Park, its a huge huge park in NW Portland, over 5000 acres, and 50 miles of trails to walk. Leif Erikson Drive starts the access to the park, from NW Thurman. If you enjoy mountain biking, this is a great place to run wild.
Forest Park has miles of trails which are great for hiking, running, or mountain biking. Park your car at the Portland Zoo lot and take off into the beautiful forest for hours of outdoors fun.