Pike Place Market is a classic Seattle tourist attractions. Explore vendors of all kinds, visit the first and original Starbucks location, eat amazing food and even walk down to the pier. This is a great launch point for an entire day's worth of activities
If you have an afternoon, taking a ferry to Bainbridge Island is a lovely way to spend it. We have one of the largest ferry systems in the world, and they are a joy to ride. Bainbridge is a very walkable town with lots of shops and great places for coffee or lunch.