Wander the waterfront!
The Seattle waterfront has something for everyone. On my first trip to Seattle I was on my own most of the time. I filled an entire two days with the waterfront. You can visit the Aquarium, eat at Ivar's, roam around Ye Olde Curiosity Shoppe, hop a Washington State Ferry for a cheap cruise to Bremerton or wherever you want to go, risk a heart attack with the Pike Hill Climb, watch a cheesy film about Mount St. Helens, buy all the bric-a-brac your heart desires, etc., etc. I could go on and on. The only thing you may get tired of is all the homeless out asking for handouts.