Discovery park is the largest park in Seattle, and is located along Magnolia bluff. While it says its closed at night, its pretty easy to sneak in and go hiking at night, which is really fun. You can also just come in the day and wander down to the beach, look at the landscaping around one of Seattle’s waste processing plants, or wander through some large grasslands.

http://www.cityofseattle.net/parks/Environment/discovparkindex.htm