Olympic Sculpture Park is part of the Seattle Art Museum, my favorite part is it's FREE, with beautiful views of Elliot Bay and the Olympic Mountains. The easiest way to walk here is, while enjoying the Seattle waterfront with all it's Piers and quirky little shops, head North, at the end of Alaskan Way you will see the entrance. For everything else you may need to know visit:
http://www.seattleartmuseum.org/visit/osp/
The cheapest way to park in Seattle is to use the meters, which now, thankfully accept debit cards. The challenge is you can only pay for about 2 hours at a time. If you go after 6pm, or on Sundays, street parking is free. If you get hungry, the Old Spaghetti Factory is on the corner of Broad and Elliot, we like the Red Robin on Pier 55, pretty amazing views for an $8.99 burger. During summer you have to get an ice cream cone at one of the many stands along the waterfront, with freshly made waffle cones!